The El Niño that took shape in the equatorial Pacific this year is on course to become the strongest in the modern record, according to forecasts from NOAA and the World Meteorological Organization.
By mid-September, sea surface temperatures in the Niño 3.4 region were already about 2C above average. NOAA's outlook puts 75% odds that the October-to-December relative index reaches at least +2.5C, a level that would exceed every El Niño in its record dating to 1950. Some models push the peak toward 3.4C above average later in the winter.
Heat stored in the ocean
El Niño is a shift in the tropical Pacific that changes where warm water sits and how the atmosphere above it moves. The warm pool that has built up this year is unusually large, and it releases heat into the atmosphere as it spreads east.
The event is unfolding on a planet already warmed by decades of greenhouse gas emissions. In August, the Copernicus Climate Change Service recorded the highest average sea surface temperature between 60N and 60S, 21.11C, surpassing a record set in March 2024. Researchers attributed the mark to El Niño on top of long-term warming.
What it means on land
Forecasters expect a wetter winter across parts of California and the southern United States, with a higher chance of atmospheric rivers and flooding. El Niño typically suppresses Atlantic hurricane activity, and this season the Atlantic has been quiet while the Pacific has produced a series of storms.
Elsewhere the signal is drier. Parts of Indonesia, Australia and southern Africa face elevated drought risk, and coral reefs in the central Pacific are exposed to prolonged heat stress. Fisheries off South America can collapse when the warm pool cuts off the nutrient-rich upwelling that normally feeds them.
The temperature ledger
2026 is already tracking as the second-warmest year on record. Because El Niño heat tends to peak in global averages with a lag, researchers expect 2027 to challenge the record for the warmest year measured.
The forecasts are also the backdrop for the COP31 summit that opened in Antalya this week, where governments are debating how to handle an overshoot of the 1.5C target. Scientists say bringing temperatures back down would require large-scale removal of carbon dioxide, not only cuts to new emissions.