NOAA has ranked the El Niño 2026 event as the second strongest on record through August, behind only 1997, and its forecasters see a very high probability that it will reach the agency’s “very strong” category through late fall and early winter. The figures come from Nat Johnson, a research meteorologist at NOAA’s Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, and a member of the agency’s ENSO forecast team, in a NOAA Satellites briefing published on October 20, 2026.
Johnson works on both sides of the forecast. He develops the lab’s seasonal prediction model and, once a month, he submits his own El Niño forecast alongside about ten colleagues at the Climate Prediction Center. The briefing runs 29 minutes and was recorded with data through August, before the agency’s October outlooks.
Second on record under a ruler NOAA adopted in February
The ranking depends on the index. The traditional Niño 3.4 index measures how much warmer the central tropical Pacific is than its own long-term average, and by that measure 2026 would already be the warmest event ever recorded. In February 2026, NOAA replaced it as its official metric with the Relative Oceanic Niño Index, or RONI, which subtracts the average warming of the whole tropical ocean belt before measuring the central Pacific. Johnson said the switch was made because the atmosphere responds to the contrast between that region and the rest of the tropics, so RONI “effectively separates the effects of ENSO from this more basin-wide warming.”
Under RONI, 1997 still leads and 2026 sits second, with data complete only through August. Johnson stressed that the ranking is provisional and that the peak of the event had not arrived when he recorded the briefing.
The older measure keeps a role. For a coral reef or a fishery, Johnson said, the local sea surface temperature may matter more than the relative one; for the winds, the rainfall and the remote impacts of El Niño, the relative index is the better guide.
The “very strong” category and the 2 °C line
NOAA declares an El Niño when the three-month RONI stays at or above +0.5 °C for five consecutive overlapping seasons and the tropical atmosphere shows the expected response: heavier rainfall over the central Pacific and weaker trade winds. Both conditions are met this year.
In September, the Climate Prediction Center added strength probabilities to its monthly outlook for the first time, splitting El Niño and La Niña into weak, moderate, strong and very strong. “Very strong” means a RONI above +2 °C, a level Johnson described as the kind of event seen “every decade or two.” His reading of the September chart was direct: there is “a very high probability that we’ll have a very strong El Niño throughout the late fall and early winter.”
The agency’s ENSO diagnostic discussion of October 8 goes further and puts an 83 percent chance on an October-to-December RONI of +2.5 °C or more, the threshold it labels historic. NASA satellite data have shown the same event pushing sea levels in the eastern Pacific up to 1.3 feet higher than normal.
One term does not appear anywhere in NOAA’s scale. The “super El Niño” of this year’s headlines is, in Johnson’s words, “an informal category that is not formally recognized by NOAA.”
What the winter map looks like for the United States
The expected pattern is the familiar one. A strong El Niño tends to bring wetter-than-average conditions across the southern tier of the United States, drier conditions over the Ohio and Tennessee valleys, and a warmer winter across the northern states and Canada. Because El Niño is the most predictable seasonal climate signal for the country, NOAA’s temperature and precipitation outlooks are historically more skillful in El Niño and La Niña winters than in neutral years, and the agency’s official winter outlook, due in October, is expected to reflect that pattern.
Timing matters as much as strength. The probabilities of a very strong event decline from late winter into spring, after the expected peak, but Johnson cautioned that many of the strongest impacts of El Niño over the United States arrive in late winter, after the ocean has already peaked in late fall or early winter.
The instruments behind the forecast
NOAA’s confidence rests on observing networks built after the 1982-83 El Niño, which arrived largely unannounced. The Tropical Atmosphere Ocean array now consists of 48 moorings anchored to the sea floor across the equatorial Pacific, measuring surface conditions and ocean temperature and salinity down to 500 meters (1,640 feet) and transmitting the data to shore by satellite in real time. The Argo program, launched in 1999, keeps more than 4,000 autonomous floats cycling between the surface and about 2,000 meters (6,560 feet) every ten days, roughly 83 floats for every TAO mooring. Satellites add sea surface temperature, sea level, winds and rainfall over an ocean with no rain gauges. The same push to observe remote waters is behind the crewless sailboats now measuring CO2 in the Southern Ocean.
How ten forecasters turn models into one outlook
GFDL’s SPEAR model issues a 12-month ENSO forecast on the first of every month, running 30 versions with slightly different starting conditions to capture the chaotic part of the climate system. Johnson compared the spread between those runs to the butterfly effect and said the forecasts are “always probabilistic.” The team also weighs the North American Multi-Model Ensemble, a set of models from U.S. and Canadian centers, because an average across different models usually outperforms any single one. It is a different route from the machine-learning add-ons that recently doubled the skill of AI weather forecasts three to four weeks out, although both rely on the same ocean observations.
Each forecaster then submits an individual outlook for ten overlapping seasons on the Monday before the release, the team votes on any change to the El Niño alert status, and the consolidated outlook goes out on the second Thursday of the month. The next one is due on November 12, 2026.
What is still uncertain
The ranking covers data through August and could move before the event peaks. The strength probabilities are odds rather than a forecast of a single outcome, and the winter pattern described here is the typical one, which individual winters have broken before. The briefing was recorded before the October 8 outlook, so the most recent seasonal probabilities are those in the Climate Prediction Center’s current discussion rather than the September chart Johnson showed.
The briefing, “How NOAA monitors and predicts the El Niño-Southern Oscillation (ENSO),” was published by NOAA Satellites on YouTube on October 20, 2026; the 83 percent figure comes from the Climate Prediction Center’s ENSO diagnostic discussion of October 8, 2026.
Video credit: NOAA.
