El Niño Sets a New Daily Heat Record, With More Strength to Come
The developing El Niño is the strongest on record in Pacific Ocean temperature monitoring. On 19 September, daily sea surface temperatures in the key central-eastern Pacific region reached 3.05°C above average, passing the previous daily record of 3.02°C above average set during the 2015 El Niño. The peak has not arrived. It is not expected until later this year, several weeks after 19 September. BBC
How the record was set
This record compares daily sea surface temperature with the long-term historical average. That comparison is known as the Oceanic Niño Index (ONI). Think of ONI as a direct reading against the past. By a second measure, the Relative Oceanic Niño Index (RONI), the current El Niño is not yet a record-breaker. An El Niño is declared when temperatures in a key Pacific region stay consistently 0.5°C above normal. El Niño is the warm phase of the El Niño Southern Oscillation (ENSO). It occurs about every two to seven years and tends to last for around a year.
What forecasters expect
Forecast guidance has converged on further strengthening. NOAA's Climate Prediction Center states El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter. NOAA For September-November through November-January 2026-27, it gives a greater than 90% chance of a very strong El Niño. The U.S. forecaster estimated a 75% chance during the October-December 2026 season of a historic El Niño event exceeding the strength of previous El Niño events. Reuters NOAA CPC has issued official ENSO Strength Probabilities for September 2026 covering El Niño or La Niña strength categories of weak, moderate, strong, and very strong.
The World Meteorological Organization said on 3 September 2026 that the El Niño weather phenomenon is set to intensify further and persist into 2027. Reuters WMO stated El Niño is firmly established and will intensify into a very strong event in the coming months, affecting rainfall and temperature. WMO forecast a nearly 100% likelihood that El Niño will persist through September-November 2026. For September-November 2026, WMO multi-model forecasts indicate an increased likelihood of above-normal temperatures across almost all land areas. Its Global Seasonal Climate Update for SON 2026 forecasts the seasonal average Niño 3.4 SST ensemble mean anomaly to reach approximately 3.6°C during SON 2026.
That outlook extends warnings issued earlier in the cycle. In July 2026, Yale Climate Connections reported that the developing El Niño could become the strongest on record. Australia's Bureau of Meteorology forecast that the developing El Niño would become the strongest on record. Met Office reporting had stated that seasonal forecast guidance suggested the developing 2026 El Niño was likely to be a very strong event. NOAA forecasters had predicted El Niño would intensify to a moderate or strong level in the fall.
What is happening now
The UK Met Office published a blog post titled 'Record-Breaking El Niño Surpasses Previous Benchmarks', authored by the Met Office, on 22 September 2026. The UK Met Office says many of the expected impacts of the current El Niño are already being felt. Professor Adam Scaife is Head of Long Range Prediction at the UK Met Office. India Meteorological Department statistics show the southwest monsoon had brought 15% less rain than normal up to 22 September. In 2026 there had been no Atlantic hurricanes as of the report date, the latest date without a hurricane forming since satellite monitoring of storms began.
The broader context here is measurement as well as magnitude. ONI captures the absolute anomaly against history. RONI adjusts for the warmer baseline. That distinction will shape how governments and risk managers interpret the word record. For practitioners, the operational signal is consistent across both: a very strong, still-growing event with persistence into next year.
Looking at the months ahead, the planning horizon is lengthening rather than narrowing. A monsoon deficit already quantified in India, suppressed Atlantic hurricane activity to a historically late date, and a near-uniform tilt toward above-normal land temperatures point to concurrent pressures on water, food systems and disaster response. With WMO pointing to persistence into 2027 and the seasonal Niño 3.4 mean near 3.6°C, the diplomacy of data sharing, forecast alignment and anticipatory finance becomes central. For international institutions, the question is less whether this event qualifies on every index, and more how to coordinate around impacts that have started before the peak.
