Three weeks ago, federal forecasters put the odds of a “super” El Niño this winter at roughly one in four. As of NOAA’s May 2026 ENSO update, those odds have doubled. The Climate Prediction Center now assigns a 37% probability that the Relative Oceanic Niño Index, or RONI, will reach or exceed 2.0°C during the November-December-January 2026-27 peak, the threshold that defines a “very strong” event. When the adjacent “strong” category (1.5 to just under 2.0°C) is added, the combined probability climbs to roughly 50%.
That is the kind of shift that gets the attention of California reservoir operators, Gulf Coast emergency managers, and grain traders in Chicago all at once. Only two El Niño episodes in the modern record, 1997-98 and 2015-16, cleared the super threshold. Both reshaped winter weather across half the globe.
Inside the numbers: what changed between April and May
The CPC publishes ENSO strength-category probabilities using RONI, a metric that replaced the older Oceanic Niño Index in recent years to better capture the spatial pattern of tropical Pacific warming. In the April 2026 outlook, the combined strong-plus-very-strong probability for the coming winter sat near 50%, but the very strong slice alone was closer to 25%. The May revision kept the combined figure in the same neighborhood while pushing far more weight into the very strong tier, from roughly 25% to 37%.
In plain terms: forecasters are not just saying El Niño will be significant. They are increasingly saying it could be historic.
What drove the shift? The CPC’s narrative discussion does not spell out a single cause, but several factors likely contributed. Subsurface ocean temperatures in the equatorial Pacific have been running well above average since early spring, building a reservoir of heat that fuels El Niño intensification. Updated sea-surface temperature observations and fresh runs of the multi-model ensemble both feed into the probability tables, and both appear to have trended warmer between the April and May initialization windows.
How this compares to past super events
The 1997-98 El Niño pushed peak ONI values (the predecessor metric to RONI) above 2.3°C. The 2015-16 event was comparable. Both episodes delivered a recognizable pattern: torrential rain and mudslides across Southern California, above-normal precipitation along the Gulf Coast, drought intensification in Indonesia and eastern Australia, and coral bleaching across the central Pacific.
But the comparison is not a carbon copy. Each El Niño interacts with background climate conditions that have changed. Global ocean temperatures in 2025-26 have been running at or near record levels independent of El Niño, a factor that could amplify the event’s reach. The 2023-24 El Niño, which peaked in the strong category, already stressed coral reefs and contributed to record global heat. A super event arriving just two years later would give ecosystems and infrastructure little recovery time.
There are also differences in the Pacific Decadal Oscillation, the Indian Ocean Dipole, and stratospheric conditions that can modulate how El Niño’s signal translates into regional weather. Forecasters at NOAA’s Geophysical Fluid Dynamics Laboratory run an experimental prediction system called SPEAR, and its April 2026 ensemble shows individual model members diverging sharply after midsummer. Some reach super territory by November; others stall in the moderate range. That spread is a reminder that the atmosphere has not yet committed to a single path.
Why the forecast is still far from certain
A 37% chance of a super El Niño is the single largest probability assigned to any strength category for the winter peak. It is also, by definition, a statement that there is a 63% chance the event falls short of that level. The remaining probability fans out across moderate, strong, and even neutral outcomes.
Spring is the hardest time of year to predict where ENSO is headed. Climatologists call it the “spring predictability barrier”: small errors in initial ocean temperatures or wind patterns can compound into large forecast differences by winter. The CPC’s next update, expected in June 2026, will incorporate another month of observations and a fresh model cycle. If subsurface heat continues to build and westerly wind bursts persist over the western Pacific, confidence in a strong-to-super outcome will likely grow. If those signals stall, the probability distribution could flatten again.
For now, the honest read is that the odds have tilted meaningfully toward a powerful event, but the forecast has not locked in.
What is at stake for food and water systems
Global commodity markets are already pricing in the possibility. Strong El Niño winters tend to reduce rice and palm oil yields in Southeast Asia while boosting wheat prospects in parts of Argentina. The 2015-16 event contributed to food-price spikes in several developing nations. A super event in 2026-27 would arrive against a backdrop of already elevated global food costs driven by supply-chain disruptions and fertilizer price volatility.
In the western United States, the stakes are more immediate. California’s reservoir system, designed to capture winter runoff for year-round use, faces a familiar dilemma: managers must leave enough flood-control space to handle intense storms while positioning to store as much water as possible for the dry season. The state’s Department of Water Resources began reviewing its winter operations plan in May, earlier than usual, citing the evolving El Niño outlook.
Across the Southwest, agricultural producers who depend on irrigation allocations from the Colorado River basin are watching closely. A wet El Niño winter could temporarily ease drought conditions in some tributaries, but the relief tends to be uneven. The 2015-16 event, for instance, delivered heavy snow to the Sierra Nevada but left the Upper Colorado basin drier than hoped.
Practical steps before the next forecast update
For communities and households in El Niño-sensitive regions, the current forecast window offers lead time that is often wasted. Coastal residents in Southern California and the Gulf states should verify flood insurance coverage now; standard homeowner policies typically exclude flood damage, and National Flood Insurance Program policies require a 30-day waiting period after purchase. Past strong El Niño winters have overwhelmed aging stormwater systems with repeated, intense atmospheric river events.
Agricultural producers in drought-prone areas should review crop insurance deadlines and water allocation contracts before midsummer, when updated forecasts will narrow the range of likely outcomes. Irrigated operations may want to assess whether infrastructure can handle both sudden surpluses and potential mid-season dry spells, a combination that strong El Niño winters have delivered before.
Energy utilities and hydropower operators face their own calculus. Heavy winter precipitation can rebuild depleted reservoir storage but also raises the risk of uncontrolled spill events that waste water and damage downstream infrastructure. Incorporating the CPC’s probability range into seasonal planning, rather than betting on a single-point forecast, gives operators room to adjust as new data arrives.
The CPC’s June 2026 update will be the next major checkpoint. By then, another month of ocean observations and a fresh model cycle will either reinforce the upward trend or pull the distribution back toward moderate outcomes. Until that update, the most defensible posture is to plan for a strong El Niño as the baseline while stress-testing systems against the increasingly plausible super scenario.
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*This article was researched with the help of AI, with human editors creating the final content.
