A deep pool of extremely warm water is available to fuel El Niño in summer 2026

In June, NOAA announced that the El Niño-Southern Oscillation—Earth’s most powerful natural climate pattern—had entered its warm phase. From the beginning, models have been predicting it will be a strong event. This animation reveals a big reason for their confidence: a deep pool of warm water building up beneath the surface of the tropical Pacific Ocean. Provided the atmosphere plays its part, these warm waters can sustain the developing El Niño.

The animation tracks 5-day-average water temperatures in the upper 1,000 feet (~300 meters) of the ocean at the equator from August 11, 2025, through June 22, 2026. Blue colors show where water was cooler than the 1991-2020 average; red colors show waters that were warmer than average. The darker the color, the more extreme the anomaly, or difference from average. 

At the start of the animation, ENSO was in its cool, La Niña, phase. The eastern half of the basin was dominated by a pool of cooler-than-average waters, but an arm of warmish water undercut it from the west at depths between 200-400 feet. The warm anomaly fizzles, however, and the cool conditions associated with La Niña re-intensify in September and November.

In late November, a stronger and deeper wave of warmth begins to cross the basin from the west. By late January, that warmth is emerging at the surface in the far eastern Pacific, ending La Niña’s lingering grip and foreshadowing the arrival of El Niño. Starting at the end of March, warmth builds again at depths of 400-600 feet in the central tropical Pacific, and a deep pool of warm waters has expanded and intensified through the summer to date. By the end of the animation, portions of the water column are 7.5 degrees Celsius or more (13.5 degrees Fahrenheit or more) warmer than average.  

NOAA declared El Niño officially underway in the first half of June.

Understanding ENSO

• Want to start from the beginning? Try What is El Niño in a nutshell?
• Can’t understand why we care so much about something that’s happening out in the middle of the ocean? Read about the impacts of ENSO on salmon; coral reefs; Amazon drought; global crop yields; rainfall in Hawaii; and hurricanes, tornados, and coastal floods in the United States.
• Wonder how we know what the temperatures are beneath the surface? Read our blogger’s love letter to an array of moored buoys.
• Curious why the warm water travels from west to east? Read about Kelvin waves in an ENSO blog post from January 2015.
• Want to know how the atmosphere reacts to—and causes—these subsurface ocean temperature patterns? Read about the coupled feedback loop that connects them.