As of 25 September 2026, El Niño is strengthening in the tropical Pacific and is expected to become a very strong event later this year, according to the World Meteorological Organization (WMO), the US National Oceanic and Atmospheric Administration (NOAA) and Columbia University’s International Research Institute for Climate and Society (IRI). WMO said on 3 September that the pattern was firmly established and had an exceptionally high likelihood of continuing through February 2027. [1] NOAA’s 10 September diagnostic discussion likewise put the chance of a very strong event in the Northern Hemisphere fall and winter above 90%. [2]
The immediate status is therefore clear at the global climate-signal level, but not at the level of a single forecast for every country. Ocean temperatures in the Niño 3.4 region have risen sharply, and the coupled ocean-atmosphere pattern is reinforcing itself. That raises the likelihood of major shifts in seasonal rainfall and temperature, as well as associated flood, drought and heat risks, while leaving the precise local outcome dependent on season, geography and other ocean conditions. [1] [2]
Key points
- WMO’s 3 September update put the likelihood of El Niño persisting through February 2027 at nearly 100%. [1]
- NOAA reported Niño 3.4 sea-surface temperatures at +1.8°C in August and a greater-than-90% chance of a very strong event in fall and winter 2026–27. [2]
- WMO said the event could reach very strong intensity before peaking toward the end of 2026. [1] [5]
- IRI’s 21 September forecast kept El Niño probability at 100% through February 2027, then lowered it to 61% by May–July 2027. [3]
- WMO forecasts for September–November 2026 show a strong Pacific signal alongside a possible positive Indian Ocean Dipole, which can modify regional effects. [4]
What happened
WMO’s August 2026 El Niño/La Niña Update, published on 3 September, said El Niño had become firmly established by mid-August. It described persistent, intensifying positive sea-surface-temperature anomalies across the central and eastern equatorial Pacific. The agency’s seasonal forecast centres saw nearly 100% odds that El Niño would continue through September–November 2026 and December 2026–February 2027. [5]
The accompanying WMO press release added observational detail. The Niño 3.4 index averaged 1.5°C above normal during May–July 2026 and reached 2.0°C above normal in July. Weekly readings later rose to about 2.2°C–2.6°C above average between late July and mid-August. WMO also reported subsurface temperatures more than 8°C above average in some areas during July and early August. [1]
NOAA’s Climate Prediction Center independently described further strengthening in its 10 September discussion. It reported eastern equatorial Pacific anomalies above 3.0°C, a Niño 3.4 value of +1.8°C in August and widespread subsurface anomalies above +10.0°C at depth. NOAA’s official outlook gave a 75% chance that the October–December 2026 season would produce a historic event, defined in that discussion as a three-month relative Niño index of at least +2.5°C, exceeding events observed since 1950. [2]
Verified background and context
El Niño is the warm phase of the El Niño–Southern Oscillation, or ENSO, a recurring ocean-atmosphere pattern centred on the tropical Pacific. WMO explains that it typically develops between March and June, reaches peak intensity between November and February, and usually lasts nine to twelve months. Its influence on global temperatures can extend beyond the period of peak ocean warming. [1]
The Niño 3.4 index is a sea-surface-temperature anomaly measure for the east-central equatorial Pacific. It is one of the standard indicators used to classify ENSO conditions. A high reading matters because ocean warming and changes in atmospheric circulation can shift the distribution of rainfall and heat far beyond the Pacific, but the index is not a direct thermometer for any particular city or country. [1] [3]
IRI’s 21 September Quick Look offers a useful cross-check on model agreement. All 22 participating models indicated further strengthening, with the event remaining very strong through winter 2026–27. The forecast assigned 100% El Niño probability from September–November 2026 through February–April 2027, 99% for March–May 2027, 90% for April–June and 61% for May–July. IRI also cautioned that model forecasts contain uncertainty and that forecast systems can differ because of starting conditions, model biases and forecaster judgment. [3]
Why it matters
A very strong El Niño increases the chance of consequential seasonal anomalies, not the certainty of a particular disaster. WMO’s September–November outlook shows an increased likelihood of above-normal temperatures across almost all land areas, while rainfall patterns display the expected broad response to a strong Pacific El Niño. The same update forecasts a positive Indian Ocean Dipole with a seasonal mean of 0.9°C and a generally warm tropical Atlantic. Those additional drivers may reinforce, weaken or redirect the usual El Niño pattern. [1] [4]
That distinction is important for communities and institutions that use seasonal forecasts. Agriculture, water management, energy systems, public health and disaster planning may face different risks depending on local rainfall and heat outcomes. WMO says national meteorological and hydrological services remain the authoritative source for official warnings and locally relevant information. [1] The current evidence supports earlier preparedness and monitoring, but it does not justify treating a global forecast as a precise local prediction.
What remains uncertain
The broad direction is unusually consistent: the event is established, strengthening and highly likely to persist into early 2027. The unresolved questions concern magnitude, timing and distribution. NOAA’s forecast of a 75% chance of a historic October–December event is a probability, not a declaration that a record will occur. IRI says models agree on a very strong event but differ on how high the Niño 3.4 index will peak. [2] [3]
Regional impacts are also not determined by El Niño strength alone. WMO explicitly says the effects vary by location and season and can be modified by the Indian and Atlantic oceans. A stronger Pacific signal can therefore coexist with contrasting outcomes between regions, or with outcomes that depart from the classic textbook pattern. [1] The forecasts cited here describe risk and probability; they do not establish that any named flood, drought or heatwave will be caused by this event.
What happens next
WMO and national weather agencies will continue updating observations and seasonal outlooks as the event approaches its expected late-2026 peak. NOAA’s next ENSO Diagnostic Discussion was scheduled for 8 October 2026, while WMO said its members and partners would keep refining regional impact information. [1] [2]
For readers, the practical next step is to follow official national and regional forecasts rather than infer local conditions from the headline intensity alone. The most reliable picture will combine the evolving Pacific measurements with forecasts for rainfall, temperature and other climate drivers in the relevant season. On the evidence available by 25 September, El Niño’s continuation into early 2027 is strongly supported; the exact severity and geography of its weather consequences remain developing claims that require continued verification. [1] [3]
