El Niño is a periodic warming of the tropical Pacific Ocean that shifts the jet stream and alters storm tracks. A very strong El Niño is active for winter 2026-27, and NOAA's October 15, 2026 outlook favors a wetter southern United States and East Coast alongside a warmer northern tier.
What El Niño Is and How It Works
El Niño is the warm phase of the El Niño-Southern Oscillation (ENSO), a recurring pattern of ocean-atmosphere interaction in the tropical Pacific. NOAA's Climate Prediction Center (CPC) tracks it through the Niño-3.4 index, which measures sea-surface temperature anomalies in a defined stretch of the central and eastern equatorial Pacific.
According to ABC7 News, El Niño develops when trade winds weaken and warm water that normally pools near Asia and Australia shifts eastward toward South America. That warming pushes the jet stream southward over North America, redirecting storms that would otherwise strike the Pacific Northwest into California and the southern United States, which typically makes for wetter winters there.
How Strong Is the El Niño Behind This Winter's Forecast
CPC issued an El Niño Advisory on October 8, 2026, reporting sea-surface temperature anomalies exceeding +4.0°C in parts of the eastern equatorial Pacific, with the Niño-3.4 index at +2.1°C at that time.
El Niño continues to strengthen, with a strong-to-very strong El Niño likely through January-March 2027, remaining greater than an 83% chance.
— NOAA Climate Prediction Center, October 8, 2026 advisory
A later reading cited by Watchers.news, drawing on NOAA's seasonal outlook, put the Niño-3.4 index at +2.4°C, with an 83% probability that the October-December average would exceed +2.5°C. NOAA said a value at or above that threshold would exceed every El Niño event in its record dating back to 1950. The two figures were measured at different points in October but both describe one of the strongest El Niño events on record.
NOAA's Winter 2026-27 Outlook by Region
NOAA released its official U.S. Winter Outlook on October 15, 2026, covering December 2026 through February 2027. NOAA National Weather Service director Ken Graham said the very strong El Niño would likely push the jet stream southward and eastward across the contiguous United States, tilting the odds toward stormier weather in the South.
NOAA Winter Outlook 2026-27 — Temperature (released Oct 15, 2026)
Region
Temperature outlook
Northern California, Pacific Northwest, Midwest, Mississippi Valley, much of the East, Alaska
Warmer than average
Parts of the Southeast, including Florida
Near-normal
Hawaii and much of the Southwest
Equal chances
NOAA Winter Outlook 2026-27 — Precipitation (released Oct 15, 2026)
Region
Precipitation outlook
Southwest through the southern tier, the Southeast and the East Coast
Wetter than average
Hawaii, much of Alaska, the northern Rockies, the Great Lakes region and the western Pacific Islands
Drier than average
Intermountain West, northern Plains, Ohio Valley, Puerto Rico and the U.S. Virgin Islands
Equal chances
NOAA's outlook also projects drought improving or ending across the Southwest, the Southern Great Plains, the Southeast and the East Coast by January 2027.
California's Experience With Strong El Niño Winters
ABC7 News notes that the severe El Niño winters of 1982-83 and 1997-98 brought homes lost to erosion, flooded communities and mudslides in California, with the 1982-83 event alone causing an estimated $1 billion in damage. The same report points to storms in March 2023 that flooded more than 100,000 acres in the Tulare Lake Basin as a more recent example of El Niño-linked agricultural flooding.
California State Climatologist Michael Anderson, cited by ABC7 News, said managing heavy storm years depends on improved forecasting, quick decision-making and monitoring of Sierra Nevada snowpack to protect public safety while maximizing water supplies.
ABC7 News cautions that El Niño does not guarantee a specific outcome for any single location: the exact landfall, frequency and intensity of individual storms ultimately determine how severe a season turns out to be, even in a historically strong event.
Questions
What causes El Niño?
El Niño forms when trade winds over the tropical Pacific weaken and warm water that usually sits near Asia and Australia shifts east toward South America, raising sea-surface temperatures and altering the jet stream, according to NOAA's Climate Prediction Center and ABC7 News.
How strong is the El Niño affecting winter 2026-27?
NOAA's CPC issued an El Niño Advisory on October 8, 2026, calling for a strong-to-very-strong El Niño with more than an 83% chance of persisting through January-March 2027; a separate NOAA-based reading cited by Watchers.news said it could become the strongest event since comparable records began in 1950.
Which U.S. regions will be wetter or drier this winter?
NOAA's October 15, 2026 outlook favors above-average precipitation across the southern tier from the Southwest to the Southeast and up the East Coast, while Hawaii, much of Alaska, the northern Rockies and the Great Lakes region are expected to be drier than average.
Does El Niño guarantee flooding or storms in California?
No. ABC7 News reports that while El Niño raises the odds of wetter, stormier winters by shifting the jet stream southward, the actual severity depends on where and how often individual storms make landfall.
When did NOAA release its 2026-27 winter outlook?
NOAA published its official U.S. Winter Outlook, covering December 2026 through February 2027, on October 15, 2026.
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