NOAA, the U.S. government's climate agency, raised the probability that El Niño will reach "very strong" status from the start of the Southern Hemisphere spring in late September to 97%. The figure appears in the ENSO bulletin released on Thursday (Sept. 10) by the agency's Climate Prediction Center and was reported by the Brazilian daily Folha de S.Paulo.
The agency also puts a 93% chance that equatorial Pacific sea surface temperatures will hold at that very high level through January, a scenario informally known as a Super El Niño. Its forecast a month earlier gave a 93% chance of a very strong event starting in September.
"During the October-December 2026 season, there is a 75% chance of a historic event that would exceed the strength of previous El Niño events dating back to 1950," the bulletin reads.
Pacific waters are already more than 3°C warmer off Peru
On NOAA's technical scale, that historic scenario means a three-month relative index (RONI) of +2.5°C or higher across the central equatorial Pacific. August readings show the buildup under way: sea surface anomalies exceeded +3°C in the eastern equatorial Pacific. In the Niño 1+2 region, off the coasts of Peru and Ecuador, water reached +3.4°C above average; in Niño 3, +2.5°C; and in Niño 3.4, the central zone used to define the event, +1.8°C. At depth, parts of the ocean column are running up to 10°C hotter than normal.
MetSul Meteorologia, a private forecasting firm based in the southern Brazilian state of Rio Grande do Sul, notes that by the traditional Oceanic Niño Index (ONI) the weekly anomaly in Niño 3.4 already stands at +2.7°C. By that measure, no event in the modern era crossed the +2°C "very strong" line so early: it happened in the week of July 8 this year, compared with Sept. 3, 1997, Sept. 16, 2015 and Nov. 24, 1982. U.S. and European climate models, synthesized by the firm, point to a peak between November and December near +4°C, a level never seen in 170 years of records.
Advisory in effect, with no guarantee of impacts
El Niño began in June and is defined by abnormal warming of equatorial Pacific waters near the coast of Peru, the opposite of La Niña. The categories follow the temperature anomaly: 0.5°C to 1°C makes a weak event; 1°C to 1.5°C, moderate; 1.5°C to 2°C, strong; and above 2°C, very strong.
NOAA keeps its "El Niño Advisory" in force and cautions that an event of this magnitude increases the odds of El Niño-type impacts, with no guarantee they will materialize or be worse than usual. The effects are already visible elsewhere: Indonesia is in extreme drought that is feeding forest fires, according to Folha, which published an image of firefighters battling flames in Palembang, in South Sumatra province. NOAA's next ENSO bulletin is scheduled for October 8.