The Pacific Ocean’s cooling phase is over, and a warming one may be next. On April 9, 2026, NOAA’s Climate Prediction Center officially retired its La Niña advisory and issued an El Niño Watch, marking the first formal signal that the climate pattern linked to hotter global temperatures, weaker Atlantic hurricane seasons, and shifting rainfall across the Americas could return before the year is out.
The agency’s latest diagnostic discussion puts the model-ensemble-based probabilistic odds of ENSO-neutral conditions at 80% through the April-to-June window, meaning the tropical Pacific has already settled back to baseline. But the numbers tilt quickly after that: El Niño becomes the favored outcome at 61% for the May-to-July period, according to the same ensemble approach, and probabilities continue to climb into late 2026 according to the CPC’s strength table. These figures represent model-ensemble-based probabilistic forecasts, not deterministic predictions, and they are revised each month as new observational data feed the models.
For farmers mapping out fall harvests, water managers stretching reservoir supplies through summer, and emergency planners already eyeing the Atlantic hurricane season, the transition matters. El Niño events historically suppress hurricane activity in the Atlantic by increasing upper-level wind shear. According to CPC seasonal outlook guidance and decades of peer-reviewed composites, El Niño winters also tend to deliver heavier rainfall to the southern United States and drier conditions across the Pacific Northwest. How strongly those patterns play out depends on the event’s intensity and timing, neither of which can be pinned down yet.
What the data actually shows
The CPC’s declaration rests on two criteria spelled out in its alert system definitions: the Niño-3.4 sea surface temperature anomaly must cross at least 0.5°C above or below average, and the atmosphere must show a matching response in tropical rainfall and trade-wind patterns. La Niña met both thresholds for months. Now neither is present, which is why the agency can simultaneously close one advisory and open a watch for the opposite phase.
Behind the classification sits a relatively new measurement tool. The CPC recently adopted the Relative Oceanic Niño Index, or RONI, which compares Niño-3.4 temperatures against the broader tropical ocean mean rather than a fixed 30-year baseline. The switch matters because background ocean warming has been gradually inflating traditional indices, making it harder to distinguish a true El Niño signal from the overall warming trend. RONI draws on the Extended Reconstructed Sea Surface Temperature dataset, version 5 (ERSSTv5), a peer-reviewed record stretching back to 1950, and is designed to keep El Niño and La Niña classifications comparable across decades.
The probability figures in the April 9 discussion supersede earlier numbers. A CPC graphic dated March 12, 2026, which circulated widely through NOAA’s drought information channels, showed El Niño odds exceeding 80% by fall. Whether the April update adjusted those figures is not entirely clear from the published documents, but the April 9 tables should be treated as the current assessment.
Why spring forecasts come with wide error bars
A 61% probability sounds decisive, but spring is the worst time of year to predict where ENSO is headed. Climate scientists call the March-to-June window the “spring predictability barrier” because subtle shifts in subsurface ocean heat and equatorial wind bursts can push the system toward very different outcomes. Models that agree reasonably well in autumn often diverge sharply during this period, and the CPC’s own confidence intervals widen as forecasts stretch into fall and winter.
There is also the question of atmospheric coupling. Sometimes the ocean warms past the 0.5°C threshold without triggering the full suite of atmospheric changes that define a textbook El Niño. These borderline or short-lived events can still influence weather patterns, but they make it difficult for forecasters to characterize the event’s strength or project regional impacts with any precision. Until trade winds slacken and tropical convection shifts eastward in a sustained way, the watch remains exactly that: an early alert, not a done deal.
The 2023-24 El Niño offers a recent reminder of how variable these events can be. That episode ranked among the strongest on record by sea surface temperature but produced regional impacts that diverged from historical composites in several areas, reinforcing the point that no two El Niños play out the same way.
What to watch as 2026 unfolds
The CPC updates its ENSO diagnostic discussion on the second Thursday of every month, and each release will refine the probability picture as new ocean buoy data, satellite observations, and model runs come in. Several milestones will signal whether this watch escalates to an advisory:
- Niño-3.4 temperatures: A sustained rise above the +0.5°C anomaly threshold would satisfy the oceanic half of the CPC’s criteria.
- Atmospheric response: Shifts in the Southern Oscillation Index, weakening trade winds, and eastward migration of tropical rainfall would confirm the ocean and atmosphere are coupling.
- Regional outlooks: The CPC has not yet issued region-specific precipitation or temperature guidance tied to this El Niño watch. When it does, those products will translate abstract probabilities into actionable planning for water supply, wildfire risk, and agricultural decisions.
For now, the practical takeaway is straightforward: La Niña is done, the Pacific is resetting, and the odds increasingly favor a warm phase taking hold by mid-to-late 2026. How strong it gets, and what it means for any particular city or crop or coastline, is a story that will sharpen month by month as the data comes in.
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*This article was researched with the help of AI, with human editors creating the final content.
