La Niña continues to weaken with forecasters now predicting a 75% chance of transition to ENSO-neutral conditions during January-March 2026.
According to the National Oceanic and Atmospheric Association‘s Climate Prediction Center, La Niña persisted throughout December 2025 as indicated by below-average sea surface temperatures across the east-central and eastern equatorial Pacific Ocean. The latest weekly Niño-3.4 index value was -0.5°C, with the Niño-3 and Niño-1+2 indices remaining cooler at -0.8°C and -0.7°C, respectively. The equatorial subsurface temperature index became slightly positive, reflecting the expansion of above-average temperatures from the western to the east-central Pacific at depth.
Atmospheric Response Still Reflects La Niña
Easterly wind anomalies were present over the central equatorial Pacific throughout December, while upper-level westerly wind anomalies continued across the equatorial Pacific. Enhanced convection persisted over Indonesia and suppressed convection strengthened near the Date Line. The equatorial Southern Oscillation index was positive, confirming the coupled ocean-atmosphere system remains consistent with La Niña.
Transition Expected Soon
The International Research Institute multi-model predictions indicate ENSO-neutral will emerge during January-March 2026. Forecasters favor ENSO-neutral to develop during this timeframe with a 75% probability. Even after equatorial Pacific sea surface temperatures transition to ENSO-neutral, La Niña may still have some lingering influence through early Northern Hemisphere spring 2026.
For longer forecast horizons, there are growing chances of El Niño, though uncertainty remains given the lower accuracy of model forecasts through the spring season.
What This Means for Winter
The weakening La Niña and expected transition to neutral conditions means typical La Niña weather patterns may become less pronounced as we move deeper into winter. The lingering influence through early spring 2026 means winter weather patterns may continue to show some La Niña characteristics even after sea surface temperatures reach neutral levels. The next ENSO Diagnostics Discussion is scheduled for February 12, 2026.
