The recent La Niña event in the tropical Pacific has officially ended, according to new updates from the United States’ National Oceanic and Atmospheric Administration (NOAA). Oceanic and atmospheric patterns now reflect ENSO-neutral conditions — a phase expected to persist through the Northern Hemisphere summer, with a greater than 50 per cent likelihood lasting into the autumn.
ENSO, or El Niño Southern Oscillation, is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean. It affects not only sea-surface temperatures (SST) but also wind patterns, atmospheric pressure and rainfall across large parts of the globe. La Niña and El Niño are the two opposing phases of ENSO.
ENSO-neutral, by contrast, describes a state where neither El Niño nor La Niña is dominant. While neutral phases tend to make global seasonal forecasts more uncertain, they are often a transitional period between the two more extreme phases.
In March 2025, NOAA scientists confirmed that conditions had shifted back to ENSO-neutral. SST in the central and east-central Pacific were no longer as cool as before. In the key Niño-3.4 region — used to track ENSO phases — the temperature was nearly average at -0.01 degrees Celsius, much warmer than the La Niña threshold of -0.5°C below normal.
This quick shift to neutral conditions happened as warm water spread westward across the eastern Pacific and the pool of cooler water below the surface began to shrink. Some signs of La Niña in the atmosphere — like strong trade winds — were still present, but without the cold surface water, the system no longer qualified as La Niña.
Looking ahead, forecasters at NOAA and the International Research Institutec said they believe ENSO-neutral conditions are likely to continue through the summer, with chances well above 50 per cent into the August-October period. Beyond that, predictions become less certain, especially during spring — a time when forecasts are less reliable due to what scientists call the “spring predictability barrier”.
Still, current projections give a 43 per cent chance that ENSO-neutral conditions will last into early winter (November 2025 to January 2026). There is a 38 per cent chance of La Niña returning, while the odds of El Niño remain low, below 20 per cent.
The recent La Niña was short and mild and did not meet the criteria to be listed in NOAA’s official records, which require five continuous overlapping three-month periods of colder-than-average temperatures. However, this season could be added to the historical record later, depending on how long-term climate averages are updated in future years.
