NOAA puts 83% odds on a historic El Niño in October–December 2026 By Carolina Costa
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The Niño 3.4 region of the equatorial Pacific Ocean recorded +3.4 °C, the highest value of this El Niño so far, according to the weekly bulletin of the National Oceanic and Atmospheric Administration (NOAA), the United States agency for oceans and atmosphere. Forecasts point to further strengthening until the peak, expected for November or December.
The bulletin was released on Monday, 26 October 2026, and the reading was 0.1 °C above the week before. Estael Sias, managing partner of MetSul Meteorologia, said every climate model analyzed shows El Niño gaining strength through November along the equatorial Pacific. On 2 November, NOAA’s Climate Prediction Center kept its El Niño Advisory in place.
Why NOAA uses two indices to measure the event
NOAA relies on the ONI index to classify a classic El Niño, the kind with global reach. Since this year, the agency also uses the RONI index, which adjusts for the warming of tropical oceans. The two indices cannot be compared directly.
- ONI in Niño 3.4: +3.4 °C, in NOAA’s weekly bulletin
- RONI in Niño 3.4: +2.5 °C, in the very strong El Niño category
- Weekly Niño 3.4 average centered on 14 October: +3.3 °C, according to the International Research Institute (IRI)
- Probability that the event beats the strongest episodes since 1950 in October to December: 83%, in NOAA’s 8 October update
Peak could reach +3.5 °C to +4 °C, with timing still open
Estael Sias said almost all projections point to maximum intensity in November or December, followed by a gradual loss of strength from early 2027. Most data place the peak between +3.5 °C and +4 °C, although some models show values above +4 °C.
Keep reading: Cemaden lowers El Niño heat wave forecast for Brazil in 2026
The IRI forecasts peak intensity for December, with an absolute anomaly of +3.5 °C in Niño 3.4 in its consolidated result.
WMO projects an average of +3.7 °C, above the 2015-2016 episode
The World Meteorological Organization (WMO) said warming should reach exceptional levels between October and December 2026. Its projection puts the average at about +3.7 °C, above the +2.6 °C recorded in the 2015-2016 episode.
- 11 June 2026: NOAA confirmed El Niño conditions, with Niño 3.4 at +0.7 °C that week
- Month before the 8 October 2026 update: anomaly of about +2.1 °C in Niño 3.4
- October to December 2026: average projected by the WMO at about +3.7 °C
Event strength does not set the size of its impacts
Estael Sias said the intensity of El Niño, measured by the temperature of Pacific equatorial waters, does not determine in proportion how large the effects on global or regional climate will be. A warmer event does not necessarily mean bigger effects everywhere, and the link between intensity and impacts is not linear. The position of the warm waters, the winds, the atmospheric circulation and the temperature of other oceans can change the response in each event.
Learn more: Cemaden cuts El Niño heat wave forecast for Brazil until end of 2026
Figures still unconfirmed: +5.2 °C and the 2023 comparison
The value of +5.2 °C in the Niño 1+2 region, off the coasts of Peru and Ecuador, cited by Estael Sias, has not been confirmed by an independent source. The claim that the 2026 El Niño is much stronger than the 2023 event also lacks confirmation, since the 2023 indices were not verified independently. The exact date of the peak remains open: Sias points to November or December, and the WMO to December.
NOAA’s Climate Prediction Center will publish its next monthly ENSO update on 12 November 2026. The update will show whether the event has crossed into historic territory.
