El Niño is here - and likely to be historic. Here's how California will be impacted
El Niño is here, and it's only getting stronger.
The National Oceanic and Atmospheric Administration on Thursday announced El Niño is present in the tropical Pacific and issued an advisory for the climate pattern that is expected to last through at least March 2027. The agency forecasts greater than 90% odds of a "strong" El Niño and a 63% chance of a "very strong" event by early winter.
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Read more: El Niño could supercharge this year's Pacific hurricane season
"That would rank among the largest El Niño events in the historical record going back to 1950," NOAA said.
The world is likely to set new heat records. This year will be among the hottest on record, and 2027 will probably end up as No. 1, the World Meteorological Organization announced.
El Niño probably won't significantly impact California's weather this summer. An enhanced Pacific hurricane season may direct larger swells, more frequent dry lightning or a rare tropical storm toward the state, but the most pronounced effects are expected this winter.
An El Niño in historic territory would favor all of California for above-normal precipitation this winter. That doesn't guarantee historic floods, but El Niño alters the position and strength of the storm track, favoring the southern U.S. in particular for more frequent winter rain. NOAA also warns of more coastal flooding due to a double whammy of more storms and higher seas.
Unusually persistent oceanic heat beyond the equator is further increasing forecasters' confidence that El Niño will bring more rain than usual to California.
It's too early to say when or where storms will hit California, but UC Agriculture and Natural Resources climate scientist Daniel Swain said "it would significantly surprise me" if this winter isn't an unusually wet one.
What is El Niño?
While El Niño impacts radiate globally, the weather shifts stem from oceanic temperature changes in the equatorial Pacific.
In the eastern tropical Pacific, sea surface temperatures were 0.7 degrees Celsius above normal in early June, above NOAA's 0.5-degree threshold for El Niño. This anomaly must persist for many months to go in the books as an official El Niño, which NOAA predicts with a 100% chance this year.
These warm waters reset global weather patterns by reshuffling heat and energy in the atmosphere.
Changes in wind and pressure in the atmospheric tropics can disrupt weather patterns across the globe. El Niño is the most powerful climate influence on global weather patterns, and the most predictable.
What are El Niño's effects on California?
Traditionally, El Niño's most pronounced impact on California's weather is on precipitation, during the wet season that runs from late fall through early spring.
The jet stream, better known as the storm track, is powered by temperature differences between the tropics and Arctic. When El Niño heats the atmosphere over the eastern tropical Pacific, jet stream winds are typically faster than normal over the southern U.S. and can spur storms in California.
This year's El Niño stands out to scientists because of its anticipated strength.
Strong to very strong El Niños favor more precipitation in all portions of California, with the more pronounced signal in the central and southern portion of the state.
"Some signal does work its way up to the Bay Area in the years with the strongest response, but it's more consistent in Southern California: Los Angeles, San Diego and inland," said Matthew Rosencrans, a meteorologist at NOAA's Climate Prediction Center.
Not all strong El Niños have been wet in California.
Notably, 2015-16 didn't soak California to the degree of the wet winters of 1982-93 and 1997-98, which brought textbook El Niño impacts to the state. That drier winter showed that while El Niño is the best predictor of California's precipitation in the long range, there are atmospheric and oceanic influences that can't be anticipated this far in advance.
Rosencrans said El Niño and California's precipitation is "not a perfect correlation." Things like atmospheric rivers, local marine heat waves or sudden warming of the polar regions can alter weather on shorter timeframes.
The extra case for a wet forecast
One of those factors is jumping out: A large region of above-normal sea surface temperatures extending from Southern California to Hawai'i all the way south to the equator. These conditions are favored to persist through the fall and winter, which could push the jet stream even farther north into Northern and Central California, too.
Long-range weather models predict anomalously wet conditions across all of California in the November through January timeframe. That includes a key blend of multiple computer predictions known as the North American Multi-Model Ensemble.
"That could be contributing to where this (wet) signal may extend further north this year, rather than if you had the same El Niño without that," Rosencrans said.
While NOAA is months away from releasing its winter forecast, Rosencrans says it's never too early to prepare, and that people should continue to pay attention to how El Niño unfolds.
Swain is more confident: "The single biggest seasonal predictor of precipitation in California is the presence of a strong El Niño."
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This story was originally published June 11, 2026 at 10:34 AM.