May 18, 2026 — The odds are in El Niño’s favor right now.
This natural weather phenomenon, part of the El Niño-Southern Oscillation, or ENSO, occurs when warmer-than-average water extends throughout most of the equatorial Pacific Ocean just below the surface. That’s happening now. And powerful bursts of westerly wind have pushed immense amounts of warm water eastward, toward the Niño3.4 region where sea surface temperature, along with other atmospheric conditions, is used to assess the state of ENSO.
On May 14, in its monthly ENSO outlook, the NOAA/National Weather Service Climate Prediction Center gave an 82% chance that El Niño will be in place for the period May through July, which implies that it’ll be here within weeks.
How do experts know when El Niño has arrived?
El Niño conditions are declared when the atmosphere and ocean are in sync and the Niño3.4 sea surface temperature is at least 0.5 degrees Celsius (0.9°F) warmer than the seasonal average.
But just as hurricanes can and do stray from the “cone of uncertainty” at times, it’s vital to remember that El Niño can do much the same. Preparing for the prototypical outcomes is a smart move, as long as you keep in mind that forecasting the El Niño-Southern Oscillation is more a matter of probabilities than certainties.
NOAA now uses a Relative Oceanic Niño Index, or RONI, in which the Niño3.4 value is adjusted relative to the world’s tropical oceans as a whole; the goal is to keep global warming from smudging the signal of El Niño and La Niña events themselves.
Nearly all seasonal forecast ensembles used to predict ENSO at agencies around the world now concur that the imminent event is likely to bring Niño3.4 warming of at least 1.5°C, which would push it into the “strong” category. And some of the ensemble averages are now going well above 2°C, even for the adjusted RONI index. That would put it in the ballpark of the biggest El Niño events in the NOAA database going back to 1950.
Individual ensemble members still cover a fairly broad range, with outcomes varying from a weak event to a record-stomping one, but as shown below, they’re about as close to being unanimous on a significant El Niño as you’re likely to see. (This output is mainly using the traditional pre-RONI index, which tends to run slightly hotter on recent El Niño events.)