“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 (+2.5°C or more for a 3-month RONI value).”
ENSO Diagnostic Discussion (September 2026)cpc.ncep.noaa.gov75% is a favourite, not a lock. NOAA puts a 'historic' El Niño this October to December (+2.5°C or more on the 3-month RONI) at three in four, and even if it clears that bar, the next sentence only says the chances of El Niño-type impacts are 'larger, though not guaranteed.'