Extreme weather whiplash continues to reshape our lives and landscapes. Nature demanded our attention again as autumn slogged into winter 2025-26, proving the difference a year can make when wild and stubborn weather anomalies force landscapes and people to repeatedly adjust and recover, while we all look toward an uncertain future. Are these game-changing battles between baneful fire and water or simply nature’s way of finding balance? Follow me on this latest natural history tour where we explore the science behind all the hype and drama. Should you decide to skim down to the very end, you will be rewarded with dynamic beach and wetlands landscapes, colorful sunsets, and some special avian visitors.
Introduction: Transmogrification in California
We need a new word to describe this. Forgive those who sense that we have entered some sort of space-time warp, when two locations and microclimates separated by just a few miles could experience such radically different atmospheres, as if they were worlds apart. But it also seems unthinkable that such remarkable changes could occur within any specific region within just one year, challenging us again to check our calendars. Old descriptors for our once more dependable seasons and weather patterns have been evolving toward unfamiliar, unlikely, exceptional, and unprecedented. Comparing the final months of the calendar years 2024 and 2025 unveils a topsy-turvy environment that repeatedly produced chaotic scenes more common to a science fiction movie.
Less than 11 months before I took this photo, vegetation on these slopes at will Rogers State Park in the Pacific Palisades was burned to the ground, along with Will Rogers’ historic ranch house. By late November, 2025 the coastal sage and chaparral plant communities were already springing back, thanks to several inches of unusually early heavy rains that quickly ended the fire season. Purple nightshade, morning glory, and other early flowers joined many crown-sprouting shrubs. By the first days of January, 2026, one year after the conflagration, the slopes were already covered with thick green blankets and colorful flowers following even heavier rains.
Several years of stories on this website have documented widely researched seasonal disorders that have made news headlines each month … and they only seem to be getting weirder and more impactful. We are, at this time in this state, perfectly situated to explore and learn from these upheavals as our unparalleled diversity of microclimates, ecosystems, and landscapes continue calling out to us.
Calendar Contrariness
One year ago, our stories led you through the unprecedented weather patterns that set the stage for catastrophic historic and deadly wildfires which eventually consumed entire Southern California communities. We examined the momentous drought that left only around 1/10th of an inch of rain in the SoCal coastal plains from spring into mid-January (the middle of our rainy season). This year stood out in stark contrast as many of those same locations had already equaled or exceeded half their average annual precipitation totals by mid-November, long before what are usually the wettest months of the rainy season. But as we advanced into November, 2025, nature performed another dramatic switch. Persistent weather patterns locked into place into mid-December and they were all powerfully connected: SoCal’s seemingly endless sun and above-average temperatures in the 80s versus consecutive days of record cold, dank, and dreary valley fog; merciless warm atmospheric rivers (ARs) from the tropics that produced record catastrophic flooding in Washington contrasted with arctic blasts that plunged the upper Midwest and East Coast into the deep freeze. Yet another radical shift near the end of December (and into 2026) brought powerful storms and flooding atmospheric rivers across California during the holiday season. The spectacular diversity of conditions and their theatrical impacts on us and our landscapes have ranged from astounding to unnerving. There’s so much going on in this story that should keep curious observers on the edge of their seats.
A mid-October winter-style midlatitude cyclone kicked off the 2025-26 rainy season surprisingly early. After skies cleared on Oct 15, slopes of the San Jacinto Mountains were already soaked with a few inches of rain. What a contrast from the last season, when these mountains remained bone dry well into January. Here, you can even see a light dusting of snow remaining at higher elevations as a few stratocumulus clouds drift in the fresh breezes behind the storm. This was just the start of an extraordinarily early rainy season in Southern California.
Episode One: Odd Cutoff Lows Spin Their Moisture Magic
Some of the blame for these multiple twists of fate (sometimes coined weather whiplash) started with a series of odd early-season cold and unstable upper-level low-pressure troughs that dug down from the north and broke off from general circulation patterns. November’s cutoff low repeat performers skimmed down the West Coast, mostly whirled and sprinkled through Northern California, taking the bulk of their moisture and energy with them. Then, the pesky, reenergized storms anchored and spun their turbulence over waters just off the Southern California Bight, entrained Pacific moisture, and tossed it inland. Give the National Weather Service credit for warning us about these cutoff lows that remain a weather forecaster’s woe.
As hours ticked into days, trains of steady showers circulated from Mexico up through and past Santa Barbara County. When the unstable moisture was lifted up the Transverse Ranges, heavier orographic precipitation watered the slopes and snuffed out the fire season. Soils became saturated, seasonal streams resumed flowing early, fresh green spouts appeared everywhere, and premature weeds erupted in our gardens. Since the showers were mostly beneficial and steady rather than sporadic downburst gulley washers, we were first spared the worst of flooding and debris flows that could have coughed out of our burn scars. Observers were wondering how it was possible that the hills were so alive just one calendar year after debilitating drought and Santa Ana winds had primed these same landscapes for their dehydrated fiery destruction. One of the wettest starts to our rainy season this year had transposed last year’s driest into our rear-view mirrors.
By mid-November, a series of low-pressure systems pinched off from upper-air circulation patterns and intensified off the Southern California Coast. They circulated copious amounts of moisture onshore, resulting in several inches of rain that broke records during this exceptionally wet November, 2025. During this break in the rain on November 16, heavy cumulus clouds were mushrooming up toward higher cloud layers, all of them announcing the arrival of air columns loaded with water. Precipitable water (PWAT) in air columns (the total amount of water contained in any column of air) repeatedly reached record levels within November and December atmospheric rivers.
Note the exceptionally deep upper-level cutoff low that stands out off the Southern California coast on this 500mb chart (showing atmospheric pressure and winds halfway up through the atmosphere). California is on the wet and unstable east side of the low, which is driving moist air from the south directly over the state. Source: National Centers for Environmental Prediction, Weather Prediction Center.
This November 15, 2025 radar sequence shows bands of heavy rain circulating up from the south, into the Southern California Bight and up against the Transverse Ranges. The circulation is directed by that same low-pressure system shown in the previous image. Source: NOAA/National Weather Service.
This satellite photo shows the same November 15, 2025 storm spinning precipitation into Southern and Central California. Notice the long connection to the tropics as the atmospheric river races across the Pacific (from the bottom of the screen) and is directed toward the West Coast. Source: NOAA/National Weather Service.
As the center of the low-pressure system passes nearby on November 18, moist air becomes unstable. Towering cumulus clouds boil into the cold air aloft, where large ice crystals grow until they fall toward the surface and melt, forming heavy showers in the distance. Higher layers of ice crystal cirrus clouds shield our view of the blue sky.
A break in the clouds appeared between turbulent impulses as the center of low pressure moved inland on November 21. Note the thin cirrus clouds drifting above flat-bottomed-puffy-topped cumulus. Look carefully to see the ripples (ribs) that have formed in horizontal waves perpendicular to the upper-level winds that are flowing toward the low.
Ocean Current Mysteries
Augmenting the improbability of these captivating whodunnits, all this early-season atmospheric chaos was raining down during the start of a weak La Niña year, when cooling water currents in the tropical East Pacific might be expected to result in more stable air and a relatively dry SoCal rainy season. Here’s more proof that the El Niño/La Niña Oscillations we research as ENSO cycles (such as in previous stories on this website) and their effects have NOT been as dependable or predictable during this century compared to late last century. We are reminded that we are observing and researching targets that are constantly moving and evolving.
A possible less-understood culprit for the October-December 2025 SoCal wetness could have been the now infamous North Pacific “blob” that peaked in September and circulated through the end of the year. This giant marine heat wave (which has reappeared in some form during recent years) expanded to 5,000 miles across the Northern Pacific Ocean until sea surface temperatures maxed out at a record 68°F (20°C). In addition to ongoing climate change, research suggests that recent decreases in air pollution (particularly sulfur dioxide) from cleaner shipping and Chinese sources have helped to clear Pacific air masses of reflective aerosols, allowing more direct solar radiation to heat ocean surfaces. Regardless, such a mysterious warm blob throws another complicating variable into our understanding of ocean-atmosphere interactions that could be responsible for these historic anomalies.
This graphic from the BBC shows the development of “The Blob” as warmer-than-average sea surface temperatures extended across the Pacific Ocean in 2025.
“The Blob” expanded to its greatest extent during September. Source: NOAA.
“The Blob” had circulated farther south by November. “Daily sea surface temperature anomalies (SSTa) in the California Current ecosystem. Color represents SSTa, with the thick black line encircling regions which are in “heatwave status”; arrows represent wind speed and direction; thin lines represent atmospheric pressure at sea level. Blue dashed line represents the US West Coast exclusive economic zone (EEZ).” Source: NOAA.
Large patches of warmer-than-average ocean water temperatures were still being measured in December, though this was supposed to be a La Niña Year. “Daily sea surface temperature anomalies (SSTa) in the California Current ecosystem. Color represents SSTa, with the thick black line encircling regions which are in “heatwave status”; arrows represent wind speed and direction; thin lines represent atmospheric pressure at sea level. Blue dashed line represents the US West Coast exclusive economic zone (EEZ).” Source: NOAA.
Episode Two: High Pressure Heat Versus Cold Fog
As if to keep us on our toes and our eyes on the skes, nature abruptly and dramatically flipped the switch again after mid-November. Massive high-pressure systems took control, building and oscillating off the Southern California coast and over the Southwest States into Mexico. The strength and extent of these tall, heavy domes of stacked air challenged seasonal records and eventually dominated the entire state. As air descended out of the monstrous fair-weather storm blockers, clear and dry became the latest curious forecast fads across most of the state, lasting an entire month through mid-December, a period which normally marks the annual start to our seasonal rains. The November air columns started out cool, but days of dry offshore flow and compressional heating pushed temperatures into the 80s along the SoCal coast and into the upper 80s in the inland valleys right into mid-December. Weather stations in the Coast Ranges (such as in the Santa Cruz Mountains) and Sierra Nevada foothills recorded high temperatures well into the 70s in the clear, dry, sinking air. Adding an additional layer of complexity, another conspicuous exception developed and stubbornly held out as the antithesis to the warm and dry: historic valley fog episodes.
The Hollywood sign appears in the distance through the palms during an offshore breeze that produced quintessential clear skies and temperatures in the 70s in Southern California on Dec 4, 2025. Further warming under domes of high pressure would push December temperatures into the 80s during this month-long break between soaking stormy periods.
As air descends under a persistent dome of high pressure over California, it is heated by compression. This satellite image from December 9, 2025 shows clear skies and dry air, especially over Southern California, where temperatures would soar into the 80s. But the Central Valley is enveloped and trapped in a shallow layer of cold low clouds and fog that have spread into Bay Area and some other northern California lowlands. Riding up and over the high pressure, an energetic atmospheric river continues to flood the Pacific Northwest. Source: NOAA/National Weather Service.
Another perfectly clear dry day greeted Southern California participants on December 6, as they celebrated the annual King Tides event. Californians up and down the coast from Oregon to the Mexican border took photographs at the exact time of highest tides and shared them online with scientists. But these astronomical high tides contrasted with a stable weather period when high pressure, small waves, and gentle offshore winds kept the tides at bay. In contrast, when the highest tides returned in early January, they joined forces with low pressure, onshore winds, and a storm surge that caused historic flooding, particularly along Bay Area shorelines.
Epic Fog Traps
The same powerful high pressure that squeezed Southwest air columns toward the surface for a month also capped a shallow layer of cold air that settled and pooled in Northern and Central California inland valleys like dense water in a vast bathtub. I’ve written on this website and in my latest California Sky Watcher book about how our Great Central Valley is the perfect winter laboratory to make valley fog (AKA as tule fog or radiation fog), which forms in place as cold, dense, heavy air often settles down to the lowest flatlands and becomes trapped for 400 miles from Redding to Bakersfield. In this latest classic episode, the valley floor had been moistened by those earlier October/November rain events; then, the air just sat down there below the inversion with little or no circulation as leftover heat radiated out, gradually cooling the air toward its dewpoint. Once the late-night air chilled to near 100% relative humidity, the moist haze turned to cold fog. Now, we have a saturated pool of air trapped in the confines of our natural oval-shaped beaker, with the Coast Ranges on one side and the Sierra Nevada Mountains on the other.
It’s clear up here in the warm, dry air. But we are looking down into winter’s classic tule (valley) fog that has settled in the San Joaquin Valley. Travelers are often stunned by sudden temperature changes of up to 30 °F when crossing the boundary between unlimited views above the inversion and near zero visibilities in the cold gray mist below. Photo by Myung J. Chun of the LA Times.
With such short daylight hours and low sun angles, weak sunlight struggled to boost temperatures above dewpoints, allowing the winter fog to further thicken during long nights until it didn’t even “burn off” during the daytime. This tule fog enshrouded the valley from late November well into mid-December, 2025. It became the star of conversations, news headlines, and memes as the cold and gray bled west through the Carquinez Strait to invade the Bay Area. As valley temperatures stalled in the 40s, Bay Area residents shivered through consecutive hazy and foggy days that could barely warm into the 50s. The dull creepy mist also condensed in other inland valleys through Central and Northern California, from wine country, to the Trinity, Klamath, and Eel River Basins. Such a remarkable and historic prolonged exaggeration of the annual valley fog doldrums was capable of depressing the most upbeat Pollyanna to beg for mercy in the form of some clear-sky relief.
Whether you call it valley, radiation, or tule fog, it all looked the same for 400 miles from Redding past Bakersfield. This is at Redding’s Sundial Bridge on December 11, 2025, near the northern extent of the weeks-long atmospheric quagmire. Temperatures hovered in the 40s F through what seemed to be endless stagnant foggy days and nights. Source: Mike Chapman, Redding Record Searchlight.
To be or not to be Fog
Though we call it “fog”, this particular weeks-long episode often formed as low stratus cloud ceilings a few hundred feet above the ground. Visibilities near the ground (and below the thicker hovering blanket) were often measured at around a mile or so, decreasing at night and slightly improving again each afternoon. Just above the inversion, at around 2,000 feet above sea level, temperatures warmed well into the 70s each day thanks to dry, sinking air and unlimited visibilities. Some mountain and foothill communities could only look down through their pristine ether toward the distant layers of thick silver cotton below. In contrast, that same descending air often scoured out any inversions trying to form in SoCal. When the high pressure strengthened overhead, the Southland enjoyed a string of iconic warm and crystal-clear December days. When the resilient high weakened or drifted a bit, a shallow marine layer was enabled to spread night and morning fog into coastal valleys. During those days, most California coastal and valley communities were mired below stagnant inversions that forced air quality management districts to issue alerts and enforce no burn days: no chestnuts roasting on open fires to belch smoke that quickly gets trapped below shallow choking anvils.
When high pressure weakened or moved just a bit, it allowed a shallow marine layer to creep in under the inversion. The result was infamous late night and early morning fog along the coast, otherwise mostly sunny afternoons. This is also when air quality management districts often declared no burn days, as air pollutants were trapped in the shallow atmospheric soup. When high pressure strengthened again and nudged inland, offshore breezes would wipe out the haze and leave brilliant clear days. The dark hill in the foreground was scorched in last year’s Palisades firestorm. Note how vulnerable the burn-scar slopes were to the downpours that would follow: welcome to mud and debris flow country.
Pollution and Fog Partnerships
Recent research shows that the frequency of cold valley fog events in California was increasing each decade into the 1980s, most likely because of increasing air pollution. Droplets of water are more likely to condense around certain particulate matter, known as cloud condensation nuclei. As emissions from fuels combustion and farm operations increased, fog episodes became thicker and more frequent. After the 1980s, as air pollution controls took effect and emissions decreased, so has the frequency of dense fog. Indeed, there is an exact correlation between NOx pollution (nitrogen oxides) content in valley air and fog density and frequency, measured both from the ground and satellite imagery. This could explain why the more recent thickest “fog” actually formed a few hundred feet above sea level, leaving the higher fringes of the valley shrouded while residents at lower elevations were looking up toward the grayest low blanket. Gradual climate change could also be playing a role when today’s warming surface temperatures remain just a degree or two above valley dew points.
Winter NOx concentrations in the Central Valley show decreasing air pollution since the 1970s. “Time series of wintertime (November–March) NOx concentration from 1962 to 2014 from the CARB archive. Color coding represents change in 1° of latitude, beginning at 40°N with cool colors representing northern cities and warm colors representing southern. ppb = parts per billion.” Source: JGR atmospheres:https://doi.org/10.1029/2018JD029419
This graph shows how pollution AND fog episodes in Fresno have been decreasing since the 1970s. “Time series of smoothed Fresno fog days from National Oceanic and Atmospheric Administration records (gray dotted line) plotted with national (square) and local (circle) emission inventories in tons per day. NOx inventories represented by shades of blue points: two national NOx inventories, ranging from 1940 to 1998 and 1970 to 2017, and one local San Joaquin Valley NOx inventory from 1960 to 2014. National PM10 estimates from 1940 to 2017 represented by green squares. Local SO2 estimates from 1975 to 2015 represented by yellow circles.” Source: JGR atmospheres:https://doi.org/10.1029/2018JD029419
Whether measured from the ground or space, the number of winter fog days in Bakersfield and Fresno have been decreasing since the 1970s. (Valley fog is absent during the warm season.) “Validation of the satellite-derived measures of fog with ground observations from the (a) Fresno and (b) Bakersfield Airports.” Source: AGU Geophysical Research Letters: https://doi.org/10.1002/2014GL060018
Is this fog or smog trapped below the early November inversion? It’s both. Since water droplets often condense around abundant particulate matter (PM) that act as cloud condensation nuclei, haze and fog are more likely to form when the air is polluted and near its dewpoint.
Essential Fog
These might seem like foggy details, but they are important for a number of reasons, far beyond casting our brooding moods; here are two. First, transportation is often crippled by dense valley fog. There is a long history of deadly California accidents caused by low visibilities, followed by scenes of multiple mangled vehicles once the mysterious murk finally begins to clear. Surviving commuters have been caught in hours of gridlock on shrouded highways and narrow serpentine detour routes. Air traffic is often diverted and delayed when even the most experienced pilots with highly sophisticated cockpit instruments are challenged while attempting to take off or land through such dense curtains of potential aviation disasters. Second, the foggy winter chill deposits some moisture and may shield valley fruit and nut trees from direct sunlight during dormant periods of rest, which eventually increases annual production of these multi-billion-dollar agricultural products. (Before native plant communities were plowed, grazed, and developed into history, winter fog played an essential role in nurturing vast valley prairies that some coined California’s Kansas.)
Tule fog’s malaise is finally broken up when restraining high pressure eases or moves away and when turbulent instability sweeps in from the Pacific, allowing wind currents to scour down to valley floors. Regardless, this latest misty atmospheric quagmire kept millions of acres and millions of Californians from the Central Valley to the Bay Area enveloped throughout a remarkable string of consecutive clammy days and nights with temperatures stuck in the 40s F.
Winter’s frigid tule fog condenses in place and seems to sit there. This photo was taken along the Sacramento River Trail on Dec 13, 2025 by Jenny Espino and appeared in Redding’s Record Searchlight. By then, countless news stories had covered the incessant widespread fog event.
Episode Three: Catastrophic Floods and Frigid East Coast Connections
We can also recognize how our resilient high-pressure blocker was part of a larger pattern that dominated weather across the continent. As air descended out of our massive high, its winds were turned to the right by the Coriolis force, creating those familiar clockwise pinwheel circulations common to all high-pressure systems that often span thousands of miles in the Northern Hemisphere. These gyrating winds curved toward big, cold low-pressure systems spinning counterclockwise in the Gulf of Alaska. Strong pressure gradients and powerful air streams grew along narrow battlefronts between the highs and lows to drive abundant moisture and embedded disturbances flowing across the Pacific within atmospheric firehoses; a parade of rainmakers were directed north, up and over California’s tall stacks of fair weather and into the stormy Pacific Northwest.
The resulting archetypal atmospheric rivers (ARs) had sources so distant and farther south of Hawaii that Mango Express replaced the more familiar Pineapple Express monikers. The prolonged invasions of unusually warm moist air strengthened to attack the Pacific Northwest. Snow levels were so high, almost all the precipitation fell as torrential mountain rain that had to runoff somewhere. Rivers surged over their banks in December until record stream gauge heights sent catastrophic flooding across landscapes and into neighborhoods from north of Portland into Canada.
On this day, storms were still riding north over the ridge of high pressure in the Southwest, where daily high temperature records were being broken. But the big ridge would gradually shift east after December 14, 2025, allowing the AR to begin sliding south, so that Pacific Northwest streams and rivers might recover from catastrophic flooding. Source: NOAA/National Weather Service.
Amplified Waves Make West Coast-East Coast Connections
How is this connected to the December artic blasts that dropped clippers of snow, ice, and wind storms across the upper Midwest until temperatures plunged below zero F and wind chills could freeze flesh within a few minutes? Once that same stream of air arched up and over our West Coast high pressure ridge, it came diving down its opposite (east) side and into the middle of the continent. This downstream trough opened the door for arctic air to race directly out of Canada and all the way to the East Coast, proving how all of these pattern shifts and winds are connected. And these high-amplitude waves in the upper-level winds are just what computer models have warned us about. As the Arctic has warmed faster than most other locations on our planet, temperature gradients and pressure gradients between warmer air to the south and cool air to the north are decreasing. The jet stream that forms between these contrasting air masses tends to slow down and form large meanders (Rossby waves) of upper-level troughs and ridges that get stuck in place and that’s exactly what happened through mid-December. Two more powerful connections in one paragraph!
Here is the satellite view looking down on the eastern US on the same day as the last image (December 14). Follow the storm track as it rides north up and over the western ridge and then slides down south, bringing frigid air into the stormy Midwest and East Coast. Source: NOAA/National Weather Service.
This 500mb chart from December 14 shows how pressure patterns had been steering upper-level winds and ARs into the Pacific Northwest up and over a high-pressure ridge dominating the Southwest. Farther east, frigid winds from Canada were plunging south, down the backside of the ridge and toward the big stormy low-pressure trough drifting across the Midwest. Weather conditions from west to east may have seemed worlds apart, but they were interconnected by these high-amplitude meandering waves.
Episode Four: Atmospheric Rivers Bring More Winds of Change
Later in December, yet another major weather pattern whiplash changed everything again. The stubborn Southwest high-pressure system finally began weakening and drifting away, allowing that historic atmospheric river to gradually, mile by mile, sag south as pressures dropped. As it shifted south, the AR whipped back and forth, targeting most of California through the holiday season. To keep your attention and prove how these winter AR storms mean business in Northern California’s high country, consider this NWS forecast on December 23, 2025 for Mount Shasta:
“Snow. The snow could be heavy at times. Low around 13. Wind chill values as low as -13. Windy, with a south wind 85 to 95 mph increasing to 100 to 110 mph after midnight. Winds could gust as high as 115 mph. Chance of precipitation is 100%. New snow accumulation of 41 to 47 inches possible.”
Unfortunately, snow levels remained very high especially early during most of these AR onslaughts, adding snowpacks only to the highest elevations, often above resort levels. A low-pressure trough forming off the coast finally bent the AR into a more southwest-northeast oriented arc to circulate copious amounts of rain and high-elevation snow into the state. As air pressure continued to drop offshore, fears of a “bomb cyclone” event grew, while pulses of damaging winds, thunderstorms, and other severe weather swung across California’s Central and North coast during the holidays.
In this Dec. 18 water vapor satellite image, you can see signs that high pressure over California and off the coast is beginning to yield to moisture and clouds drifting ahead of the atmospheric river that will drop into California. Source: NOAA/National Weather Service.
By December 20, the AR firehose has gradually shifted south over Northern California, where drenching warm rains would dominate the weather for days. Source: NOAA/National Weather Service.
By December 20, persistent high pressure finally weakened and drifted east, allowing the marine layer to thicken. Onshore flow carried warm, moist air masses off the Pacific and encouraged increasing clouds (such as these stratocumulus) to drift inland. As pressures dropped, we could anticipate the arrival of the latest atmospheric river as far south as Southern California.
By December 21, a developing low-pressure trough off the coast tilted the AR into a southwest-northeast alignment. This circulation would usher in exceptionally moist, warm air masses from south of Hawaii into California. Resulting turbulence would finally break the back of the valley fog and set the stage for a two-week long series of drenching storms and ARs that would flood south all the way into Southern California. Source: NOAA/National Weather Service.
And as the bullseye finally migrated into Southern California, this AR was following recent patterns, behaving much like computer models have also warned: as global temperatures increase, warmer water can evaporate into warmer air that has the capacity to hold more water vapor. These trends are loading ARs with moisture and energy since the air can hold about 7% more water vapor for every 1°C increase in temperature (about 4% more water vapor for each 1°F). Recent single AR events have produced more than a foot of rain as they get lifted over higher terrain. In this holiday episode, such orographic effects dumped more than a foot of water into rain gauges from north of Santa Barbara along the Transverse Ranges into the San Gabriel Mountains. Where ARs had stalled over them, some weather stations had already received their average annual rainfall totals even before the two normally wettest months (January and February) of the season. As expected, flooding and debris flows belched out of the mountains, particularly below recent burn scars. The resort communities of Wrightwood and Lytle Creek in the San Gabriel Mountains earned most of the media attention for mudflow destruction (see links to videos following these essays). With a few exceptions, many of these fitful storms lost much of their punch while trying to slip south toward San Diego County, bringing mostly lighter and beneficial precipitation there.
By December 23, a major winter storm and its AR was flooding most of California. Wind barbs and flags were added to this satellite view to show the direction of winds at low to high altitudes. Note the influx of warm, moist air from the south and into California on the right side of the middle latitude cyclone. Far out in the Pacific, on the right side (behind) of the cyclone, you can see cold air flowing down from the north. This pattern would be repeated for nearly two weeks as a series of exceptionally wet Pacific storms moved through. Source: NOAA/National Weather Service.
During the same day (Dec. 23) as in the previous satellite image, flags flapped, trees bowed, and thick clouds streamed in the stiff south-to-north winds blowing into and ahead of a deep low-pressure system that was approaching from the northwest. We could sense the tropical nature of the warm, moist air as it circulated off the Pacific and overhead. Heavy rains quickly followed. These archetypal pre-storm surface conditions were repeated as several additional storms approached and swept through the state into the New Year. (But forecasts can get tricky if a cyclone approaches from the southwest, instigating backing winds to blow more from the east and off the dry land. In those cases it takes some time for precipitation to moisten lower-altitude air masses enough so that the rain won’t evaporate before reaching the surface.)
Wind direction and speed are shown (flags and barbs) with these satellite images that span about five hours during December 24. Source: NOAA/National Weather Service.
Reiterating the power of atmospheric connections (again), upper-level winds dipping around the low-pressure trough that directed firehoses to blast California through the Christmas season were forced to turn back north over a massive high-pressure ridge dominating the central US. Air descending out of this monster dome of high pressure set countless records for both the hottest high and highest low temperatures ever recorded during the holiday season, from Arizona, Utah, and New Mexico, across the Rocky Mountains, through the Plains and Midwest and into the southern US. Temperatures peaked at 20-35°F above the average in many of these regions (high temperatures in and around Oklahoma City made it past 80°F) while some Californians were getting washed out.
On December 24, a deep low-pressure trough dominated off the West Coast, directing wet storms into California. But connected meanders in the upper-level waves and jet stream curved up and north of the dominant high-pressure ridge anchored over the middle of the country. Record holiday-season temperatures soared more than 20 °F above average throughout the West, South, and Midwest US. Source: National Centers for Environmental Prediction, Weather Prediction Center.
It would be difficult to overstate the difference between the start of last year’s rainy season and this 2025-2026 season, especially in Southern California. (The official water season begins on October 1 each year.) The parade of holiday storms continued across California through the first few days of January, raining on the Rose Parade for the first time in 20 years and cancelling celebrations into the New Year’s Weekend. Contrast this year’s drought-breaking and eventual deadly inundations with virtually no rain by this time last year and the deadly fires that followed. On January 1 alone, more than one inch of rain fell from Oxnard to Long Beach, setting new records for the date. By early January, 2026, numerous locations from north of Orange County to the Central Coast Ranges had already equaled or exceeded their average annual rainfall totals, just as the two traditionally wettest months of the year were to begin. Some stations (such as in Santa Barbara County) experienced their wettest start just after last year’s record driest start to any rainy season. On the first days of January this year, freshwater runoff coincided with another astronomical King Tides event, causing historic shoreline flooding (such as around the Bay Area), when the tides combined with low pressure, onshore winds, and storm surges. You can see why we can only guess what surprises to expect in the long run, so stay tuned.
Epilogue: Following the Science that Connects the Dots to our Future
This story’s roller-coaster ride analysis of interconnected phenomena guides us into 2026, as we hope to settle back into more seasonable expectations; but nature likely has other plans. If you want to imagine 2026 and beyond, click back to some of 2025’s extreme weather events, such as those analyzed in our other recent website stories (rogue storms, Texas flash floods, SoCal wildfires, etc.). What do they all have in common? Though we were warned a few days ahead by remarkably accurate forecasts from the National Weather Service, the deadly catastrophes went on to destroy too many lives and too much property, often because local officials failed to properly prepare and respond.
As a trough of low pressure sent drenching rains to flood California during the holiday season, the upper-level winds curved back north and over a massive high-pressure dome that anchored above the middle of the country. Record high temperatures over 80 degrees were experienced all the way up into the Great Plains in the days just before Christmas, with many locations recording their warmest Christmas ever. It was another example of how connected high-amplitude kinks in upper-level Rossby waves and jet streams can become stationary, creating prolonged periods of anomalous weather conditions.
We have learned that anything goes as we anticipate beyond those seven- and ten-day forecasts, and the mysteries grow as we look further into the next year. So, we wonder why, at this critical time when we must better comprehend the science behind what is rocking our world, the US Government is cutting the heart out of the very scientific organizations that help us make sense of these changes and anticipate what might be next. As I write this, the latest victim to be thrown on the chopping block is the National Center for Atmospheric Research (NCAR) in Colorado. Should we lose this and other vital agencies that objectively and efficiently guide us through the science of change and warn us what to anticipate, we all become victims. What took us decades to build and nurture may be lost forever. Such short-sided penny-wise and pound-foolish irreversible policies are certain signs of a less developed society in decline, a culture that celebrates ignorance only to suffer the long-term consequences.
We could be forgiven for behaving like the frogs in the pot parable, except these are not gradual changes; they’re slapping our faces and kicking our butts every season. Changes that have always ruled our world have been growing in intensity and duration and these coalescing change agents are calling out for our immediate attention. Like uninvited intruders in our homes, such massive experiments are repeatedly and more frequently transforming our environments and our lives to remind us that we ignore them—and nature—at our peril.
Christmas Day storms eased just long enough to allow this rainbow to decorate the skies over Santa Monica Bay. Low-angle morning sunlight managed to peak through a break in the clouds so that it could shine into a rain shower headed toward the Santa Monica Mountains in the distance. (If you dare look for more, continue past the following brief list of links to find a chronological sequence of colorful images from space and the ground.)
For you dedicated weather enthusiasts and researchers who are hungry for even more discussion and details, continue on past this brief list of links, where you will find a chronological sequence of dynamic images from the last months and days of 2025.
A wealth of additional images (from the ground and from space) and maps follows, carrying you through some of the more memorable and dynamic weather events and colorful scenes from late 2025. Captions are limited, but they are also in chronological order. This journey (we could consider it an appendix or addendum) incudes some details that should interest meteorologists and climatologists AND instruct newer students and casual observers. We will make it all the way to the start of 2026 and a break in the stormy weather, ending our photo ops with sunsets, moon rises, flowers, and feathered friends.
Revisiting Episode One (October-November, 2025): Odd Cutoff Lows Spin Their Moisture Magic
By October 15, 2025, an unusually early season rogue storm off the Pacific had already dumped inches of rain across California. Here, the storm had cleared San Gorgonio (Banning) Pass the following day, leaving some stratocumulus clouds behind. But this residual moisture wouldn’t make it to the dry rainshadow sides of the mountains or into the desert resorts beyond … on this day.
An early and unusually deep upper-level low-pressure trough guides wet middle latitude cyclones into California on November 14. In contrast, note the adjacent fair-weather high-pressure ridge over the middle of the continent. Source: National Centers for Environmental Prediction, Weather Prediction Center.
This water vapor image from November 14 shows a large trough off the California coast. That large elongated swirl just offshore is a gathering storm, guiding an atmospheric river. Source: NOAA/National Weather Service.
By November 15, the surface low was sweeping into Central and Southern California, carrying its weather fronts and confronting high pressure just to the east. Source: National Centers for Environmental Prediction, Weather Prediction Center.
A surprisingly large and strong cyclone had formed by November 15, stalling and circulating moisture and instability just off the Southern California Bight. Source: NOAA/National Weather Service.
By November 16, much of Southern California was still under the influence of a giant wet low-pressure system, streaming a rich mixture of clouds over us. This is viewing south.
Also on November 16 (looking to the northwest), moist, conditionally unstable air masses must rise when they encounter the mountains. This lifting builds thicker clouds to produce orographic precipitation on the windward slopes and higher peaks.
By November 18, the center of this large storm’s counterclockwise circulation can be seen near Pt. Conception. Source: NOAA/National Weather Service.
The air became unstable as the core of the closed low passed nearby on November 18. Rising air columns developed into icy towering cumulus to produce more showery weather.
As expected, the unstable air columns got another boost upward when they were forced to ascend over the mountains. Some towering cumulus clouds developed into cumulonimbus and thunderstorms farther inland.
By November 19, one storm moved on east while another was forming with an AR to our west. Source: NOAA/National Weather Service.
The National Weather Service used this graphic on November 19 to warn us that another unusually wet November storm was on the way. Source: NOAA/National Weather Service.
By November 20, this water vapor image showed another elongated low-pressure trough plunging south right off the coast. Source: NOAA/National Weather Service.
By November 21, the 500mb chart showed a closed low over California that looked similar to the one from just a week earlier. Source: National Centers for Environmental Prediction, Weather Prediction Center.
Even the surface weather map showed a storm sweeping into Southern California (Nov 21) that looked incredulously like the one from one week earlier. Source: National Centers for Environmental Prediction, Weather Prediction Center.
On November 21, another strong, wet impulse was aiming at the coast, following on the heels of the first wave of downpours that had passed to our east. Source: NOAA/National Weather Service.
The good news about being caught between storms on Nov 21 is that we got to admire the potpourri of clouds forming in the moist, unstable air.
Revisiting Episodes Two and Three (December 9-10): High Pressure, Dry Heat Versus Cold Fog AND Catastrophic Floods Versus Frigid East Coast Connections
High pressure over the West steered warm ARs into the Pacific Northwest on December 9. As the upper-level winds raced toward the east, they dove back into a trough in the midsection of the country, directing extremely cold and stormy weather out of Canada all the way to the East Coast. Source: NOAA/National Weather Service.
This is another view (on December 10) looking down through the stagnant high-pressure dome that orchestrated stable weather over California for nearly a month. Some snow is evident along Sierra Nevada ridges (the early storms were warm, bringing mostly rain), but the resilient shallow valley fog stands out as it creeps into the Bay Area and even into Northern California’s river valleys. Source: NOAA/National Weather Service.
In this water vapor image (same date as the previous Dec 10 image), the yellow swirls signal very dry air and high pressure around Southern California extending into Northern California. But serious turbulence and big changes are brewing out in the Pacific. Source: NOAA/National Weather Service.
Revisiting Episode Four (December 20, 2025-early January, 2026): Atmospheric Rivers Bring More Winds of Change
Follow Us to the End-of-Story Bonus Colors: Rainbows, Trash, Cloud Murals, Sunset, Wetlands, Flowers, Birds, and the Return of El Sol.
The National Weather Service warned again about big changes in the days ahead and possible record-breaking holiday season storms. Source: NOAA/National Weather Service.
By December 20, pressures were dropping throughout California as a powerful atmospheric river began sliding south through the state. Do you think this bird sensed that thickening clouds along the Southern California coast were harbingers of a long, wet and wild holiday season?
By December 21, Northern California was already getting drenched as the AR gradually pivoted south. Source: NOAA/National Weather Service.
By December 21, the AR firehose was flowing over the Bay Area, steered between the big low-pressure system circulating counterclockwise off the Pacific Northwest and high pressure just to our southeast. Source: NOAA/National Weather Service.
By December 23, the flow of moist air had pivoted to impact the entire state. Source: NOAA/National Weather Service.
By December 24, a massive trough of low pressure just off the coast was directing a series of storms and ARs into the state. Source: NOAA/National Weather Service.
A closeup of the storm on December 24. Source: NOAA/National Weather Service.
Run the water vapor image movie to view the dynamics of this wet system. Source: NOAA/National Weather Service.
This sequence displays the dynamics of this immense storm system. Source: NOAA/National Weather Service.
Another closeup. Source: NOAA/National Weather Service.
By December 25, several bands of rain (or impulses) were spinning around the trough and over the state. You can see the extent of this massive trough off the coast during this Christmas storm that broke some records. Source: NOAA/National Weather Service.
On Christmas Day, radar tracks a band of heavy rain that looks very familiar when atmospheric rivers slink along the coast. Trains of heavy showers bump against the Transverse Ranges, where they are lifted up south-facing slopes, resulting in extremely high rainfall totals. Expect extreme flooding when such ARs stall over one area. This is not a normal holiday for NWS forecasters. Source: NOAA/National Weather Service.
Here’s another view of this rainbow that formed below Christmas Day showers as the sun peeked through an opening in the clouds behind us. Sunlight is refracted when it enters millions of raindrops at an angle, reflected off the back of the drops, and refracted again as is comes out of the drops and returns toward our eyes. Such primary rainbows form at about 42 degrees from our line of sight. Since longer wavelengths near the red side of the spectrum are refracted at lesser angles and shorter wavelengths on the blue side of the spectrum are refracted at greater angles, the colors are separated into ROYGBIV.
This rainbow lifeguard tower stood under a break in the storm on Venice Beach as if to mimic real rainbow colors in the previous image. The red, orange, yellow, green, blue, indigo, and violet (ROYGBIV) are painted in perfect rainbow order.
One negative consequence of these downpours is that they flush pollution off the streets and into the ocean. Swimmers and surfers are warned to stay out of the water for a few days until bacteria levels return to normal.
During heavy rains, the mix of plastics and other trash from our streets mixes with the debris flushed out from burn scars. Breaking surf and longshore currents eventually redistribute the mix down the coast.
This concerned beachgoer is picking up plastics and other trash that were coughed out of this drainage during the storm. Notice the canyon that was cut into the sand as runoff rushed out to sea.
A worker and his tractor’s beach rake scooped up the debris deposited along the strand line before it could get carried out by the next high tide. A lone surfer dares to test bacteria levels after the storm.
Cumulus cloud towers decorate the sky behind Venice Boardwalk during a break between Christmas rain showers. Look carefully for the mural featuring cumulus clouds!
Yet another building along the Venice Boardwalk celebrates cumulus clouds that seem to mimic the background sky on December 25.
Meanwhile, more cumulus clouds tower above the San Fernando Valley, reaching toward high ice crystal cirrus during this rainswept Christmas.
By December 26, an AR was drifting to the southeast out of California, followed by another impulse. Source: NOAA/National Weather Service.
Another wind direction and speed big picture as the storm moves though.
Compare this radar sequence to the day before and you can see how so much rain (up to a foot) can fall along Transverse Range slopes during just one day during these atmospheric river events. Source: NOAA/National Weather Service.
The passing trough brought even more bands of rain across California on the day after Christmas. Source: NOAA/National Weather Service.
It’s only December 28, 2025 and the ceanothus has exploded with early blooms. Note the green grass, another sign that persistent early rains have soaked these landscapes in Griffith Park. Also notice how recent storms have swept the air clean, allowing clear views of older burn scars and the saturated San Gabriel Mountains and Mt. Wilson in the distance.
In contrast to last year, it’s already green on this side of the hill in late December at Griffith Park, thanks to about a foot of rain since October. California poppies, lupine, and other native wildflowers are struggling to find spaces between the crowds of opportunist weeds.
Yet another warm wet storm was approaching from the south on December 29.
Incredibly, the 2025 holiday storm hit parade just kept on coming. NWS forecasters were interpreting models and doing their best to nail down the timing and intensity of each rain event that increasingly impacted already saturated slopes and burn scars.
This water vapor image shows another soaker rotating in on the last day of the year. It promises to rain on holiday plans and the Rose Bowl Parade.
Storm clouds streaming up from the south dumped more rain on December 31.
The large New Year’s cyclone finally starts moving toward the coast, pushed east by another deep trough approaching from the northwest.
Different views of the storm that kicked off 2026.
The rain paused and clouds parted just enough by the afternoon of January 1, 2026 to encourage a long walk (the next six photos) at Bolsa Chica Wetlands in Orange County …
These ripples formed perpendicular to moist upper-level winds (blowing away from us) that roller-coastered over Orange County on January 1. Lower stratocumulus are leftovers from the storm that cleared out earlier in the day.
Bladderpod (Peritoma arborea) mixes with Coast Sunflowers (Encelia Californica) and they’re all blooming following the early rains.
Sunset reflects off the wetlands as we look toward the ocean, distant queued-up cargo ships, and middle-level clouds drifting above it all.
Viewing toward the east, the moon peeks through middle-level atmospheric waves. We also notice turbulent cumulus banking against distant mountains and pushing up into some pileus (cap) clouds.
Building cumulus get sheared by winds blowing off the ocean from left to right. Thinner layers of altostratus clouds are seen far behind them, as yet another storm system approaches from the northwest.
Look carefully toward Catalina Island to see distant towering cumulus framing the sun on the far horizon. On January 1, El sol has already begun its annual migration back toward the northern hemisphere. As it rises and sets slightly more to the north (right here) each day, we should be experiencing our wettest months of the year. But we’ve learned to expect the unexpected in recent years.
Decades of legal battles and restoration efforts at the Bolsa Chica Ecological Reserve have made this a haven for wildlife searching for rest stops, new homes, and dinner. You can watch the tides flowing in and out of these wetlands where some oil is still extracted after a storied petroleum industry history left its marks on the landscape. White Pelicans (Pelecanus erythrorhynchos) migrate here to escape harsh winters up north (likely from Canada or the Great Basin). You think the big birds you see here might be congregating with other avian species for some sort of New Year’s party, celebrating the calm between storms? And now that I’ve introduced yet another spinoff research opportunity, you can get started with maps and more info about white pelicans at the Audubon and here.
By January 5, the long series of Pacific storms were breaking up over and around Southern California, though one more impulse was sweeping rain and mountain snow across Northern California. Pressures were forecast to gradually rise throughout the week until a welcome period of high pressure and fair weather would give the state a chance to dry out. Here, cumulus clouds drifted with the onshore breezes, scattering a few showers as they banked against local mountains. Note the strand line left behind when storm debris was deposited during very high tides. You can also see tracks from the beach rake that cleared much of the debris.
