Record El Niño Has California Bracing for a Winter of Floods, Storms and Coastal Chaos

The El Niño now building in the Pacific is already the strongest on record by almost any measure, and the scientists who called it months in advance are warning California that the hardest part hasn't arrived yet.

As of mid-October 2026, climate scientist Daniel Swain — who writes the Weather West blog and works with UC Agriculture and Natural Resources — puts statewide confidence of a wetter-than-average winter at '90% to 95%,' with the biggest precipitation spike most likely in January and February. All 10 of the major climate models, he said, 'are singing roughly the same tune.'

This year's tilt in the odds toward wet and stormy conditions in California will be profoundly unsubtle.— Daniel Swain, climate scientist, UC Agriculture and Natural Resources

As of October 8, the National Weather Service's Climate Prediction Center put the odds of a 'strong-to-very strong' El Niño event running through January–March 2027 at better than 83 percent, Newsweek reported. Swain's Weather West analysis goes further, saying the event has already become the strongest on record and that further strengthening remains likely before it peaks — most probably in December, though anywhere from late November to January is possible.

What makes this moment unusual is how early the signal appeared. According to Weather West, nearly all major predictive models locked onto a historically strong El Niño as early as mid-spring — well before the traditional window of reliable forecasting — and have now been validated. Swain described purely physics-based models predicting a historically strong event six months out and then having that prediction verify as 'genuinely pretty amazing.'

It's walking like an El Niño, and it's talking like an El Niño. So far, it is all systems go.— Daniel Swain, climate scientist, UC Agriculture and Natural Resources

The mechanism driving further strengthening right now is a powerful westerly wind burst — a key process in El Niño's intensification. According to Weather West, these bursts can cause a temporary leveling of sea surface temperatures as evaporation cools the immediate ocean surface, which has sparked social media speculation that El Niño is weakening. Swain says that reading is wrong: the net effect, seven to fourteen days after a wind burst, is additional warming as upwelling is further reduced and warm water is pushed farther east. Weather West reports that the current wind burst could last longer than two weeks and may even flip the direction of the prevailing tropical winds altogether — which the outlet describes as 'exactly what we'd need to see to give El Niño that last shove into record-shattering territory.'

Californians watching for early signs of the wet season should not read a quiet October or November as evidence the forecasts were wrong. Weather West is explicit: there is 'little physical or statistical connection' between autumn precipitation and even an extremely strong El Niño. The storm-track signal barely begins to emerge by November and may not arrive until December — but once present, it is likely to persist well into 2027, through at least March.

When the storms do arrive, AccuWeather meteorologist Peyton Simmers told Newsweek to expect a more dominant southern storm track bringing multiple atmospheric rivers — long, narrow corridors of concentrated water vapor in the atmosphere that, when they make landfall, can release that moisture as heavy rain or snow. Simmers said these can lead to flooding rainfall, heavy mountain snow and landslides, and noted that the storm track may initially focus on Central and Northern California before shifting toward Southern California, including Los Angeles and San Diego.

This might be another winter, but on steroids. This might be a year when the Hollywood version of bad weather in California actually ends up coming true.— Daniel Swain, climate scientist, UC Agriculture and Natural Resources

The list of potential impacts Swain outlined during a virtual public session includes torrential downpours, rain-instead-of-snow events at lower elevations, flooding, temporarily elevated sea levels, severe thunderstorms, and even isolated tornadoes. Coastal flooding drew particular attention from Swain, who pointed out that a Kelvin wave — a pulse of warm water triggered when tropical trade winds slow or reverse — had already traveled along the coast and pushed sea levels up by more than a foot. A second coastally trapped wave is moving up the coast and was expected to reach California within roughly three weeks of his mid-October briefing.

Swain flagged Thanksgiving week and Christmas as specific windows of concern, when king tides coincide with the elevated baseline sea level. Swain warned that highways and interstates running through low-lying coastal areas could face disruption, saying if there's a major storm, major or even record-breaking coastal flooding could occur, and it wouldn't even take an extreme storm.

California has already seen El Niño's fingerprints this year. According to Weather West, near-shore water temperatures reached record levels, record-breaking coastal humidity and humid heat hit Southern California in late summer, coastal erosion and flooding from unusually elevated ocean water levels have been increasing, and multiple tropical storms and hurricanes have indirectly affected central and southern parts of the state since July.

For the Sierra Nevada, the picture splits sharply by elevation. Simmers told Newsweek that snowpack is expected to be above average for most of the range, with up to a foot of snow possible at a time during individual storms. But Swain cautioned that lower elevations could receive more rain than snow, and said he would not count on November or December for reliable Sierra snow. South Lake Tahoe, he said, could see rain almost all winter, while the highest elevations — above roughly 8,000 feet — are likely to have a very snowy winter, with potentially enormous accumulations at the tops of ski runs.

For Southern California specifically, the potential anomalies are the largest. The multi-source reporting indicates that places like San Diego could see double or more their normal rainfall, according to international multi-model ensemble data Swain has been analyzing — data he described as unlike anything he had seen before.

Why it matters — A record-strength El Niño is on track to bring California its most intense winter storm season in decades, with flooding, coastal inundation, and infrastructure disruption possible from December through March — and the window to prepare is narrowing.

Reported by kqed.org, weatherwest.com, sfchronicle.com, newsweek.com