El Niño strengthens: what it means for autumn and winter in Italy and Europe

One of the main things to observe in the coming months will be El Niño, a natural weather phenomenon that develops in the Pacific Ocean. Linked to a change in wind regimes, it allows warm waters to move eastward, releasing an enormous amount of heat into the atmosphere. The World Meteorological Organization forecasts an average Pacific surface temperature anomaly in the Niño 3.4 region of around +3.6 °C for the September-November quarter. The phenomenon is expected to continue to intensify until reaching its maximum between November and December.

The US NOAA also indicates a further strengthening of the phenomenon. In the September 10 update, the agency assigns a greater than 90% probability that El Niño will reach an intensity defined as “very strong” during the Northern Hemisphere autumn and winter. Surface temperature anomalies exceeding 3°C above average have already been observed in the eastern equatorial Pacific. Below the surface, in some areas, anomalies exceed 10 °C.

For Italy, autumn 2026, according to the picture drawn by the Lamma-Cnr Consortium, promises to be warmer than average but still uncertain in terms of rainfall. The Copernicus Climate Change Service update for September-November 2026 shows a clear signal towards high seasonal atmospheric temperatures over much of Europe, including Italy, with precipitation more likely in the southern and western sectors. "But it is not possible to make a reliable forecast of a rainy autumn, nor to say that we will have three continuously hot months", reported Francesco Meneguzzo, commissioner of the Lamma-Cnr Consortium.

Also according to meteorologist Mattia Gussoni of IlMeteo.it, between autumn and winter 2026-2027 Europe and Italy could feel the indirect effects of a possible "Super El Niño". The phenomenon originates in the Pacific, but through atmospheric teleconnections it can modify the currents at altitude up to our latitudes. This could favor milder seasons than normal and reduce the frequency of typical cold outbreaks.

The real unknown, underlined by IlMeteo.it, "lies in the overlap of El Niño with global warming of anthropic origin". The phenomenon "will act as a thermal accelerator on an atmosphere already saturated with energy." According to Gussoni, "In Italy, crossing with the waters of the Mediterranean which have recorded exceptionally high temperatures, this dynamic will drastically increase the risk of extreme weather events, such as torrential rains, flash floods and the fearsome Medicane (from the union of the English words Mediterranean and hurricane), events which are becoming increasingly frequent on our coasts. This combination of factors threatens to further exasperate the impact of climate change on our territory". The effects on Italy and Europe, however, "will not be immediate and will be largely shaped and attenuated by different atmospheric dynamics". For this reason it will be necessary to follow the evolution of the phenomenon in the coming months.

For the winter the uncertainty increases. In the September 10 update, Copernicus indicates a greater probability of above-average temperatures for the December-February period. The first sign is therefore that of an overall milder winter than normal on the continent. The picture is less clear for precipitation. Copernicus predicts wetter-than-average conditions across much of Europe, while the signal is weaker at the northern and southern edges of the continent.