Copernicus reports record September temperature in key El Niño region

Copernicus reported on 12 October that September 2026 set a sea-surface temperature record in the Niño 3.4 region of the equatorial Pacific, a key area used to monitor El Niño. Its monthly average of 29.70°C signals an exceptionally strong event, but the climate service says the reading does not yet establish that this is the strongest El Niño on record.

The record matters because El Niño is still developing. Japan's Meteorological Agency (JMA) expects the strongest conditions to continue into boreal winter and forecasts a further rise in temperature in the Pacific region it monitors. That projected peak has not happened yet.

What the September Pacific records show

Copernicus said its September Niño 3.4 reading exceeded the peak temperatures recorded during the strong 1982–83, 1997–98 and 2015–16 El Niño events. The comparison concerns the temperature measured in that region; it is not, by itself, a ranking of the entire current event across every measure of El Niño strength.

JMA reported a separate record in the Niño 3 region. It measured September's sea-surface temperature anomaly there at 4.0°C above normal, exceeding its previous record of 3.6°C from December 1997. JMA's record series begins in 1949, and the agency said El Niño conditions have persisted in the equatorial Pacific since spring 2026.

Copernicus told AFP that warmer oceans associated with climate change complicate comparisons with earlier El Niño events. It said a newer index that accounts for warming across the tropical oceans had not yet put the current event above previous ones. The agency described September's values as exceptionally strong, particularly with the expected peak still ahead, while stopping short of calling the event the strongest ever.

How long strong El Niño conditions may last

In its outlook updated on 9 October, JMA said the strongest El Niño conditions were virtually certain to continue until boreal winter. It forecast that the temperature of the Niño 3 region would keep rising until then and that the event would likely peak at a record level during the season. Those are predictions about coming months, separate from September's observed record.

JMA's latest observations show significantly above-normal sea-surface and subsurface temperatures in the central and eastern equatorial Pacific, with below-normal temperatures in the western part. It also reported weaker-than-normal trade winds over the central equatorial Pacific. Together, those observations underpin its assessment that El Niño conditions have persisted since spring.

Where September weather matched El Niño patterns

JMA identified several September weather patterns consistent with past El Niño events. It reported above-normal temperatures from the southern Philippines to Java and across parts of Africa, South America and Australia. It also identified below-normal rainfall in parts of northern South America, Southeast Asia and northern Australia.

The agency reported cooler-than-normal conditions in southern South America and southern Polynesia, and above-normal rainfall in southern Argentina and nearby areas. These observations show where weather resembled past El Niño patterns; they do not establish that El Niño alone caused conditions in any particular place.

The September record also came amid exceptional global warmth. Copernicus put the month's average surface air temperature at 16.27°C, making it the second-warmest September in its ERA5 dataset. Across oceans between 60°S and 60°N, it recorded a September average sea-surface temperature of 21.05°C, above the previous September high of 20.92°C set in 2023.

Copernicus estimated September's global air temperature at 1.63°C above the 1850–1900 pre-industrial average, the second consecutive month above 1.5°C in 2026. That is a monthly measurement, not a finding that the Paris Agreement's long-term warming threshold has been crossed. Copernicus director Carlo Buontempo said the run of months above 1.5°C was likely to continue into 2027 as El Niño intensified, while the scale and duration of any overshoot remained subject to human action.

In western Europe, Copernicus reported a joint-warmest September, tied with 2023 at 2.51°C above the 1991–2020 average. It also documented widespread dryness and record-low September river flows in parts of the Rhine, Danube, Vistula and Garonne-Dordogne, with disruption to navigation, water supply and agriculture in several countries. These are reported conditions, not a claim that El Niño alone produced them.

What remains uncertain about El Niño's ranking

September's measurements establish records in two specified Pacific monitoring regions. The agencies' different regions and methods, along with the effect of longer-term ocean warming on historical comparisons, leave the overall ranking unsettled. JMA's winter peak remains a forecast; further observations will show how high its monitored temperatures rise and how long the strongest conditions persist.