A Record El Niño Is Building in the Pacific. Here’s What It Could Mean for Winter in the U.S.

Off the coast of Ecuador and Peru this fall, the Pacific Ocean has been running more than 7 degrees Fahrenheit warmer than normal. In places, the warmth reaches far below the surface: at depth in the eastern Pacific, water temperatures are more than 18 degrees Fahrenheit above average. Satellites show the sea itself bulging upward, as much as a foot higher than usual in some areas, because warm water takes up more room. Along the equator, a band of overheated ocean now stretches for thousands of miles, from the middle of the Pacific to South America.

That band is El Niño, and by several measures it is already the strongest on record. On October 15, NOAA released its outlook for the coming winter, and the message was blunt. “A very strong El Niño will likely bring a southward and eastward shift to the jet stream for the contiguous U.S., which tilts the odds toward stormier weather across the South,” said Ken Graham, director of NOAA’s National Weather Service.

For the United States, that points to a winter of two halves: a wetter, stormier South from California to Florida, and a milder North. It could mean drought relief across much of the Southwest and Southern Plains, with floods and mudslides as the risk that comes with it. Snow lovers in the northern Rockies and Great Lakes may be disappointed. Here is what the forecasts say as of mid-October 2026, how sure forecasters are, and what past giant El Niños did.

How strong is it?

NOAA declared El Niño on June 11, 2026. It has grown stronger nearly every month since. In its October 8 update, NOAA’s Climate Prediction Center reported that the key Niño-3.4 region of the central Pacific averaged 2.1°C (3.8°F) above normal in September, with eastern regions running 3.0°C and 3.9°C above normal. By the week of October 13, the Niño-3.4 reading had climbed to +2.4°C. The atmosphere has joined in, too. The trade winds that normally blow from east to west along the equator have weakened, rain clouds have shifted east toward the central Pacific, and the Southern Oscillation index, a measure of air pressure across the Pacific, is strongly negative.

Other agencies see the same thing. Japan’s Meteorological Agency said that in September its Niño-3 index reached +4.0°C, beating the +3.6°C record set in December 1997, the highest since its records began in 1949. On October 13, Australia’s Bureau of Meteorology reported a weekly relative Niño-3.4 value of +2.81°C, the highest in its weekly series, which goes back to 2008. That beat the previous peak of +2.78°C, from November 2015. “We are currently witnessing an El Niño event that is unprecedented in the historical record,” Zeke Hausfather, a climate scientist at Berkeley Earth, told the BBC.

Forecasters now use a measure called the Relative Oceanic Niño Index, or RONI. It subtracts the general warming of the whole tropical ocean, so that a modern El Niño can be compared fairly with older ones. On that scale, NOAA gives an 83 percent chance that the October to December average will reach +2.5°C or more, beyond any El Niño since 1950. The NWS office in La Crosse, Wisconsin, summed it up in its winter briefing: this event “will rival 1982-83” as the strongest since 1950. The famous events of 1991-92, 1997-98 and 2015-16 each peaked at a RONI of about 2.1°C.

The models agree. In September, all 22 climate models tracked by Columbia University’s International Research Institute for Climate and Society gave El Niño a 100 percent chance of lasting through the winter, and nearly all of the physics-based models had the Niño-3.4 index above +3.0°C during the fall and winter. NOAA’s own Geophysical Fluid Dynamics Laboratory called its October forecast “stronger than any observed in at least 30 years,” with the 1997-98 event a close second.

How warm water in the Pacific rearranges American weather

Normally the trade winds pile warm water up in the western Pacific, near Indonesia, while cold, nutrient-rich water wells up along South America. In an El Niño, the trades weaken or even reverse. Huge, slow pulses of warm water called Kelvin waves slide east along the equator. NASA’s sea level satellites spotted the first one near Micronesia in January 2026. “Kelvin waves are like the heartbeat of El Niño,” said Josh Willis, a sea level scientist at NASA’s Jet Propulsion Laboratory. “And our sea level satellites let us peer into the ocean and watch every beat.”

When the warm water reaches the central and eastern Pacific, the heavy tropical rain moves with it. That shift acts, in NOAA’s words, “like a boulder dropped into a stream.” It disturbs the flow of air between the tropics and the middle latitudes, and that changes the jet stream over North America. In an El Niño winter, the Pacific jet tends to stretch farther east and run lower across the southern United States, steering a busier train of storms into California, the Southwest, the Gulf Coast and the Southeast. The northern states, cut off from much of that storm traffic and from Arctic air, tend to be warmer and often drier.

What NOAA’s winter outlook says

NOAA’s outlook for December 2026 through February 2027 follows the classic El Niño pattern closely. Warmer-than-average temperatures are favored across northern California, the Pacific Northwest, the Midwest, the Mississippi Valley, much of the East and Alaska. For November through January, the Climate Prediction Center puts the highest odds of a warm season over the upper Mississippi Valley, the Great Lakes and southeast Alaska. Near-normal temperatures are most likely along the Gulf Coast and in Florida. Much of the Southwest is a toss-up.

For rain and snow, the outlook favors a wetter-than-average winter across the whole southern tier, from Southern California and the Southwest through Texas and the Gulf states to the Southeast, and up the East Coast. The strongest wet signal is over Florida and the Southeast. Drier-than-average conditions are favored in the northern Rockies, parts of the Great Lakes, much of Alaska and Hawaii. The Ohio Valley, which is often drier than normal in El Niño winters, has equal chances of a wet or dry season this time.

These maps show odds, not amounts. A 50 to 60 percent chance of a wet winter in Florida still leaves a real chance of a normal or dry one. NOAA also does not try to predict seasonal snowfall, because individual snowstorms cannot be forecast more than about a week ahead.

The South gets the storms

For California, the Southwest, Texas and the Gulf Coast, a strong El Niño usually means a parade of Pacific storms. That is welcome after dry years, but heavy rain on parched, fire-scarred ground runs off fast. “While higher chances of rain and snow may bring relief to drought-afflicted areas, too much precipitation on dry soil can fuel destructive flash floods and mudslides,” Graham warned. “Now is the time for communities and individuals to plan ahead for the upcoming winter.”

The Southeast and Florida have the strongest wet signal in NOAA’s outlook. In past strong El Niños, the same storm track brought coastal storms and outbreaks of severe weather across the Gulf states. The 1997-98 winter was marked by tornadoes in Florida and the Southeast, though scientists still argue over how much of that was El Niño’s doing. This winter the National Weather Service will also start using “Particularly Dangerous Situation” wording in select blizzard and ice storm warnings, for rare storms of historic severity.

A milder North, and drought that moves

Across the northern tier, the likeliest outcome is a mild winter with fewer deep cold snaps and, in the northern Rockies and parts of the Great Lakes, less precipitation than usual. The last El Niño gave a preview. The winter of 2023-24, during a strong El Niño, was the warmest on record for the Lower 48, averaging 37.6°F, 5.4°F above normal. North Dakota, Minnesota, Iowa, Wisconsin, Michigan, New York, Vermont and New Hampshire each had their warmest winter on record.

A mild winter does not mean no winter. The La Crosse forecasters noted that “El Niño will not be the only player,” and that temperatures could swing widely, with snowstorms that cannot be forecast this far ahead. Cold outbreaks still happen in El Niño winters. They are just less likely to settle in.

The drought picture follows the same split. NOAA expects drought to improve or end by the end of January across the Southwest, the Southern Great Plains, the Southeast and parts of the East Coast. In the northern Rockies, northeastern Oregon and eastern Washington, drought is favored to develop or worsen. A wet winter can transform the desert Southwest. In Death Valley, it takes rare rain to leave the shallow pond whose paper-thin ice pushes the sailing stones of Racetrack Playa across the mud.

What it means for snow and ski season

For skiers, a strong El Niño tends to split the West from north to south. The ski snow site SnoCountry looked at how 164 western resorts did in the six strong El Niño winters since 1980 and found that the clearest winners were in the south. Ski Apache in New Mexico averaged 72 percent more winter precipitation than normal in those winters, Bear Mountain in Southern California 52 percent more and Arizona Snowbowl 48 percent more. The Pacific Northwest, British Columbia, Montana and the northern Rockies leaned drier. The Sierra Nevada and central Rockies sat in between and swung from year to year. SnoCountry calls this “a lean, not a forecast.”

Colorado, coming off what OpenSnow meteorologist Sam Collentine called a “historically low snow season” in 2025-26, tends to land near normal in El Niño winters. Across eight snow-measuring stations near major Colorado resorts, the median El Niño winter finished at 106 percent of normal snowpack on March 31. The pattern was “a solid start, a weak middle, and a stronger end.” Warmth is the wild card everywhere. In a mild winter, storms that would bring snow to high slopes can bring rain lower down.

A quiet Atlantic hurricane season

El Niño has already left its mark on this year’s hurricane season. It increases wind shear over the Atlantic, which tears developing storms apart. As of October 17, the 2026 Atlantic season had produced nine named storms and just one hurricane, Isaias, which became a major hurricane. The season’s total storm energy was 83 percent below the 1991-2020 average. NOAA’s August update gave a 75 percent chance of a below-normal season. The Climate Prediction Center notes that every Atlantic hurricane season during a strong El Niño since 1950 has been below normal.

The eastern Pacific has been the opposite. Warm water there helped fuel an unusually busy season, including Hurricane Polo, a Category 3 storm that flooded Puerto San Carlos in Mexico’s Baja California Sur in late September. The Atlantic season does not officially end until November 30, and as forecasters always remind coastal residents, it takes only one landfall to make a bad year.

Lessons from 1997-98, 2015-16 and 2023-24

The closest comparison is 1997-98. That winter, storms battered California and the southern states, while the northern half of the country had a very warm winter with below-normal precipitation and snowfall. A 1999 study by climatologist Stanley Changnon tallied 189 deaths from El Niño-related weather, many of them in tornadoes, and about $4 billion in direct losses. But Changnon also counted the benefits: lower heating bills, no spring floods in the North, record construction and retail sales, no major Atlantic hurricane damage, and an estimated 850 lives saved by the lack of harsh winter weather. He put those gains at about $19 billion. Forecasts in summer 1997 had warned what was coming, and California’s preparations cut its losses. The earlier giant, 1982-83, killed 161 people nationwide and caused $2.2 billion in damage in 1983 dollars.

The 2015-16 El Niño is the cautionary tale. It was one of the strongest on record, and Californians hoped it would break a punishing drought. Northern California and the Sierra did get a wet January. But by early February, the coastal corridor from Santa Barbara to San Diego had received less than 75 percent of its normal rain since October. “El Niño—even one as strong as this one—is no guarantee of rainfall for southern California,” NOAA’s Climate.gov wrote at the time. “It just tilts the odds.”

The 2023-24 event, besides delivering the warmest winter in U.S. records, came in wetter than average overall: nationwide precipitation was 0.92 inch above normal, though the northern tier and parts of the Great Lakes and Southwest stayed dry. Big events in the Pacific can shift weather around the world in a single season. The eruption behind the Year Without a Summer did it from the sky instead of the sea.

How sure are the forecasters?

Very sure that El Niño will be strong this winter, less sure exactly what it will do. NOAA’s Climate Prediction Center expects El Niño to last through March to May 2027, with neutral conditions favored by late spring. Its strength forecast puts the most likely December-to-February RONI near +2.4°C, with a 90 percent range of about +1.6°C to +3.1°C. NOAA’s GFDL model suggests the event is near its peak and will start to weaken by early winter. But the lab’s forecasters add that “even as El Niño may weaken throughout the winter, its impacts may continue to intensify, including over parts of the U.S.”

The biggest uncertainty is how a record El Niño behaves in a warmer world. The BBC noted that this year’s warmth is spreading well beyond the usual El Niño zone, into the wider Pacific and the Gulf of Mexico. The World Meteorological Organization says there is no evidence yet that climate change is making El Niño events stronger or more frequent. And size is not destiny. “Stronger El Niño events increase the likelihood of El Niño-related climate anomalies, but do not necessarily equate to strong impacts,” the La Crosse forecasters wrote. With an event this big, the Climate Prediction Center says, the chance of El Niño-like impacts is larger, “though not guaranteed.”

The next ENSO update is due November 12, and NOAA will refresh its winter outlook on November 19. Until then, the ocean is sending its message the same way it did in 1997, a slow pulse of heat across the Pacific. Scientists who drill into old ice, like the team at Camp Century in Greenland, read climate’s past in layers. This winter, Americans may get to watch a chapter of it being written as it falls.

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