A strengthening El Niño is shifting the odds toward wetter-than-average conditions across the southern United States and East Coast during winter 2026–27, according to NOAA. The Climate Prediction Center (CPC) reported that the latest weekly Niño-3.4 sea-surface temperature anomaly had reached +2.4°C (+4.3°F), while warmer-than-average conditions are favored across much of the northern United States.
El Niño strengthened further across the equatorial Pacific in September 2026, and NOAA’s Climate Prediction Center (CPC) said on October 8 that the October–December Relative Oceanic Niño Index (RONI) has an 83% chance of reaching at least +2.5°C (+4.5°F)—a level that would exceed previous El Niño events in its record dating to 1950. The World Meteorological Organization (WMO) separately forecast a Niño-3.4 anomaly of approximately +3.7°C (+6.7°F) for the same period.
A new Climate Impact Lab assessment estimates that heat associated with El Niño could contribute to 451 000 additional deaths worldwide from June 2026 through February 2027, including 239 000 ± 11 000 during September 2026–February 2027. The September 23 report comes as NOAA measurements show central Pacific sea-surface temperatures reaching levels last seen during the 2015–16 El Niño, while multiple media reports indicate a new daily temperature-anomaly record.
California Governor Gavin Newsom proclaimed a statewide emergency on September 21, 2026, to accelerate preparations for potential flooding, landslides, coastal hazards and other winter impacts as a strengthening El Niño develops in the tropical Pacific. NOAA said there is a greater than 90% chance the event will become very strong during Northern Hemisphere autumn and winter 2026–27.
The Northern Hemisphere polar vortex is forming normally over the Arctic and was stronger than average by NASA’s wind diagnostic in mid-September 2026. The developing very strong El Niño could favor atmospheric wave patterns that weaken the vortex later in winter, with seasonal guidance showing a possible weakening during January and February 2027.
The Climate Prediction Center (CPC) raised the probability of a historic-strength El Niño during October–December 2026 to 75% on September 10, up from 69% in August, after the coupled ocean-atmosphere event strengthened further across the tropical Pacific. CPC also raised the probability of a very strong event during the same three-month period from 95% to 98%.
El Niño is forecast to strengthen to very strong intensity during late 2026, with the World Meteorological Organization (WMO) indicating an exceptionally high likelihood of nearly 100% that El Niño conditions will persist through February 2027. NOAA’s Climate Prediction Center (CPC) separately gives a greater than 90% chance of a very strong event during Northern Hemisphere fall and winter 2026–27. A very strong El Niño increases the likelihood of major shifts in rainfall and temperature patterns across many regions, although the severity of impacts varies by location and season.
El Salvador declared a nationwide Red Alert for meteorological and agricultural drought on August 25, while Honduras expanded its drought Red Alert from 75 to 103 municipalities on August 26. Panama also declared a national state of emergency under Resolution No. 102-26 in response to El Niño-related risks, including drought, flooding and landslides. The measures come amid rainfall deficits, prolonged dry periods and increasing water stress as El Niño continues to strengthen.
The daily average sea surface temperature across the extra-polar global ocean, between 60°S and 60°N, reached 21.1°C (70°F) on August 22, 2026, the highest value in the Copernicus Climate Pulse record beginning in 1979. The reading exceeded the previous daily record of 21.09°C (69.96°F), set in March 2024, and came in August, although temperatures across the domain normally reach their annual maximum in March and April.
NOAA’s Climate Prediction Center (CPC) has raised the probability of a very strong El Niño during late 2026, increasing the likelihood of characteristic El Niño impacts across the United States during winter 2026–27. Current seasonal guidance favors wetter-than-normal conditions across much of the southern tier and drier conditions across parts of the Northwest and northern United States, while above-normal temperatures are favored across much of the West, northern tier and parts of the East.
The probability of a very strong El Niño during October–December rose from 81% in CPC’s July assessment to 95% in August, with a 69% chance that the Relative Oceanic Niño Index (RONI) will reach at least +2.5°C (+4.5°F), a level that would exceed previous El Niño events in NOAA’s record dating to 1950. The strength and location of tropical Pacific warming and convection will influence how closely winter 2026–27 follows established El Niño patterns.
