The possibility of a strong El Niño in the Pacific Ocean is increasing, raising concerns that Southern California may be in for a heavy rain season.
There is now an 82% chance that El Niño could occur in the next few months, up from a 61% chance estimated last month. And there is now a 96% chance that the weather pattern — characterized by warm ocean waters in the central and eastern tropical Pacific — will hold this winter, the National Weather Service's Climate Prediction Center said Thursday.
It remains to be seen how strong this iteration of El Niño will be. There is a 37% chance that it will be “very strong” by the end of the year, up from a 25% forecast released last month.
There is also a 30% chance that El Niño will be “strong,” a 22% chance that it will be “moderate,” and a 9% chance that it will be “weak,” forecasters said.
Several forecast models suggest “a very good El Niño,” according to Marty Ralph, director of the Center for Western Climate and Extreme Waters at the Scripps Institution of Oceanography at UC San Diego.
“It has a very good chance of being modestly above the El Niño threshold, and possibly much higher,” he said earlier this week.
(Paul Duginski/Los Angeles Times)
Just three weeks ago, the World Meteorological Organization said it saw a clear change in temperature in the equatorial Pacific, which is an indication that the arrival of El Niño is near.
“There is great hope for the onset of El Niño, followed by further strengthening in the following months,” Wilfran Moufouma-Okia, head of the weather forecasting agency, said in a statement. “The models show that this could be a powerful event.”
He noted, however, that forecasts are ongoing and subject to change. But Thursday's announcement indicated that the chances of a strong El Niño continued to rise.
El Niño is one of the most powerful weather events on Earth, capable of reshaping the global climate and affecting rainfall and drought, according to the WMO. It usually hits every two to seven years and lasts about nine to 12 months.
A typical El Niño is linked to higher than average rainfall in Southern California, according to the National Weather Service. A strong El Niño can shift the jet stream that usually brings rain from the forests of southern Mexico and Central America to California and the southern United States.
While it's not a given that El Niño will bring a heavy rain season to Southern California, some of the strongest patterns in the past have been monsters.
There have only been three “stronger” El Niños in the past half century, in 1982-83, 1997-98 and 2015-16. The first two brought heavy and devastating rain to the Golden State.
In early 1998, hurricanes brought widespread flooding and mudslides, causing 17 deaths and more than half a billion dollars in damage in California. Downtown LA received nearly a year's worth of rain in just one month. At least 27 homes were so badly damaged that they couldn't safely stay on the beach, according to the California Coastal Commission.
In the winter of 1982-83, the damage was worst along the coast as huge waves came up between strong storms. An estimated $100 million in damage was reported. The US Army Corps of Engineers reported that 33 coastal homes were destroyed and another 3,000 homes, along with 900 coastal businesses, were destroyed by storms, waves, erosion and other forces.
But the El Niño of 2015-16 – while strong in the equatorial Pacific – did not bring the expected results of rain in Southern California, and failed to bring the state out of a punishing five-year drought. That water year actually saw below average rainfall in the region, and average or above average rainfall in Northern California.
However, that El Niño “caused significant coastal erosion on many California beaches,” according to the Coastal Commission.
The effects of the El Niño of that period were more significant in other areas. There has been a “record-breaking hurricane season in the central North Pacific,” with 16 tropical storms in an unusually warm ocean — more than three times the average, according to the National Oceanic and Atmospheric Administration. It's also the worst drought in the Caribbean – so much so that 65% of Antigua's farmers are out of business, and the 1-billion-gallon reservoir is dry.
There is a big star about El Niño. Since 2000 or so, Ralph said, “the traditionally expected relationship between El Niño, La Niña, Southern California and wet winters has gone in a different direction.
During La Niña, sea surface temperatures in the central and eastern Pacific Ocean cool – the opposite of the El Niño trend. The jet stream also shifts north, often pushing winter storms toward the Pacific Northwest and Canada while leaving areas of California drier than average, especially in the south.
Ralph put together a scientific paper that sought to understand exactly why 2010-11, 2016-17 and 2022-23 were the wettest years in California despite the presence of La Niña. As it turns out, El Niño and La Niña aren't the only players in determining how much rain and snow falls in Southern California.
The El Niño/La Niña pattern likely influences some storms that hit California, but only the typical seasonal type from Alaska or northern Hawaii, Ralph said. What El Niño and its cold sibling pattern do affect, however, are “atmospheric rivers,” which can carry more rain to California from the tropics, Ralph said.
Those types of storms have been increasing in recent years, fueling the strongest winter storms even without the presence of El Niño.
For example, last fall brought another La Niña, and the prospect of a dangerously dry winter in Southern California. Instead, the season was wetter than average. .
But the 2023-24 El Niño, which was described as “strong,” brought a good wet year to Southern California, with the city of LA receiving 155% of its normal annual rainfall. That February, there was a record rainfall and an unforgettable five days of rain in a row that caused hundreds of mudslides in LA alone. Dozens of houses and buildings were damaged by the debris flow, including 15 houses that had red tags.
Although El Niño does not always work as expected in Southern California, some experts still find it important to use its arrival as an event setter for possible climate impacts. El Niños are usually associated with heavy rainfall in southern parts of South America, central Asia and the Horn of Africa, according to the World Meteorological Organization and the National Weather Service. It is also associated with dry weather in Washington, Oregon, Idaho and Alaska, and the Ohio River Valley in the Midwest and upper South, as well as in Australia, Indonesia and parts of southern Asia.
In the event of a strong El Niño, it could mark the team with a deep ocean heat wave continuing along the West Coast. Both that ocean warming and any incoming El Niño will “impact animals, fish, birds and marine mammals,” said Andrew Leising, a research oceanographer at NOAA's Southwest Fisheries Science Center.
“In general, warm water – whether it is a heat wave in the ocean or due to El Niño – leads to a lower productivity of the ecosystem at the bottom of the food web, and therefore there is less food around and up the food chain for our large animals, fish, birds, etc.,” said Leising.
Leising said he expects the current ocean heat wave, which will begin to fade between October and December, to be extended by the arrival of warmer ocean waters from El Niño.
He doesn't expect we'll see “hotter temperatures” and the combination of an ocean heat wave and El Niño, “but I wouldn't be surprised if we break some records this fall, if only by small margins.”
Scientists don't know much about the cumulative effects of a warm ocean wave. One result is that “they tend to make the surrounding prey deeper in the water,” since they don't really like warm water near the surface, according to Leising.
“Let's say we keep this heat in SoCal, and this is rolled into the heat from El Niño during the fall and winter. That would be a long time for the animals to be exposed to these warm temperatures, so not only will they have less food, but the warm heat alone can be a problem for some of them,” he said.
The current ocean heat wave technically started in May 2025, slowed as expected last fall, but never retreated to the coast and stayed in Southern California, Leising said.
“Then it expanded again in December and until now, and it's been stuck there around Southern California. This is not a normal pattern.”
