El Niño explained: what is driving the record-strong 2026 Pacific event

El Niño is a periodic warming of surface waters in the central and eastern tropical Pacific Ocean, driven by a weakening of the trade winds that normally push warm water toward Asia. When those winds relax, warm water sloshes back toward South America, altering atmospheric pressure patterns and shifting rainfall and storm tracks across much of the globe.

Why it is in the news in October 2026

NOAA's Climate Prediction Center said in its ENSO Diagnostic Discussion that El Niño is strengthening, with a greater than 90% chance of a very strong event persisting through the Northern Hemisphere fall and winter of 2026-27. The agency's data show sea-surface temperature anomalies above 3.0°C in the eastern equatorial Pacific, with the Niño-1+2 region measuring +3.4°C, Niño-3 at +2.5°C and Niño-3.4 at +1.8°C as of late August. NOAA puts the odds at 75% that the October-December three-month index will exceed +2.5°C, which would surpass every El Niño on record dating back to 1950.

Climate scientist Daniel Swain said the anomaly, measured on the ONI scale, is far beyond anything previously observed, according to Inside Climate News, which reported the event tied the 1997-98 episode on NOAA's relative ONI (RONI) index by late August before continuing to strengthen through September.

How 2026 compares with 1997

Columbia University's Climate School reported that models from its Center for Climate Systems Research and the International Research Institute for Climate and Society point to tropical Pacific temperatures reaching 3.38°C above average at their November-to-January peak, versus 2.37°C above average during the 1997 event's peak. Climate scientist Muhammad Azhar Ehsan said most of the 22 models used in the forecast reach or exceed 3°C, pointing to an exceptionally strong event, while colleague Andrew Robertson said the certainty behind the forecast was itself unprecedented.

The Hill reported that Ehsan separately noted the atmospheric evolution of trade winds in 2026 closely resembles the pattern observed in 1997, when one of the strongest El Niños on record formed. That event contributed to a chaotic 1997-98 winter in North America: ice storms hit the Northeast while California and the Southeast saw severe flooding, California and North Dakota recorded their wettest winters since 1895, and a January 1998 storm killed 56 people across the U.S. and Canada while leaving millions without power, per The Hill's reporting.

What the strength could mean

The Climate Impact Lab, a research group that studies climate risks, estimated that the current Super El Niño could be linked to roughly 451,000 additional heat-related deaths worldwide between June 2026 and February 2027, compared with a typical year, with about 239,000 (plus or minus 11,000) of those deaths projected within the first six months. The estimate, built from temperature-mortality relationships across 24,378 regions combined with ECMWF seasonal forecasts, lists Nigeria (31,400), Sudan (17,500) and Niger (10,000) among the countries facing the largest projected tolls, alongside Indonesia, India, Brazil and parts of Southeast Asia.

The same research group said proven measures, including heat warnings, cooling centers and targeted health outreach, could prevent tens of thousands of deaths if deployed quickly. Columbia's Climate School separately noted the 1997-98 El Niño was linked to roughly 23,000 deaths and tens of billions of dollars in damage worldwide through crop failures, flooding, fishery collapse and mass coral bleaching.

Regional impacts being forecast

According to Columbia's Climate School, forecasters expect El Niño-linked drought risk to rise across northern South America, Central America, South Africa and Southeast Asia, while above-normal rainfall is expected across the southern United States, lower South America, East Africa, the Middle East and the United Kingdom. Inside Climate News reported that U.S. West Coast impacts could include roughly one additional foot of temporary sea-level rise along the California coast through December, a wetter-than-average winter for Southern California, and a doubled likelihood of coastal flooding during peak tidal periods, prompting advisories from authorities in Los Angeles and Britain.

NOAA's Climate Prediction Center said it will issue its next ENSO diagnostic update on October 8, 2026, and that current forecasts give El Niño conditions close to a 100% chance of persisting through the winter before an expected transition toward neutral conditions in spring 2027.