May 2026 was the second-warmest May on record, Copernicus reports, as an early heatwave swept Western Europe
Global average surface air temperature reached 15.81°C last month, 1.42°C above pre-industrial levels, while an unusually intense heatwave brought summer conditions to France, Portugal, the UK and Ireland weeks ahead of schedule.
Global temperature milestone
May 2026 was the second-warmest May ever recorded globally, both over land and sea, according to the EU's Copernicus Climate Change Service (C3S). The global average surface air temperature reached 15.81°C, which is 0.55°C above the 1991–2020 average for the month. Only May 2024 was warmer in the ERA5 dataset, which extends back to 1940. The month's temperature was 1.42°C above the estimated pre-industrial average for 1850–1900.
May 2026 was the second-warmest May on record globally, extending the period of exceptional heat worldwide, with near-record temperatures in both the atmosphere and the ocean. In Europe, an unusually early and intense heatwave demonstrates how quickly extreme climate phenomena are becoming the new normal, rather than an exception.
An early-season heatwave across Western Europe
The month was marked by a rapid transition from much-cooler-than-average conditions to one of the most intense heatwaves ever observed so early in the year in Western Europe. Within days, the continent shifted from relatively cool weather to temperatures typical of mid-summer. Copernicus noted that the situation became "particularly difficult" in France, the United Kingdom, Ireland and Portugal, where thermometers climbed far above seasonal norms and numerous new monthly records were set.
Ocean temperatures and the approaching El Niño
Sea surface temperatures were exceptionally high in the tropical Pacific during May, as the equatorial Pacific continues its transition toward El Niño conditions. El Niño is a naturally occurring phenomenon, appearing every two to seven years, in which weakening trade winds lead to warming waters in the eastern Pacific. Its effects include rising global temperatures and irregular precipitation patterns, bringing drought to some regions and heavy rainfall to others.
- ENSO index in neutral phase at 0.5°C above average; IPMA issues update
- Forecast models show transition to El Niño beginning (82% probability by July)
- El Niño conditions expected to persist through end of year (probability above 90%)
El Niño forecast for the months ahead
Portugal's Institute for Sea and Atmosphere (IPMA) released an update on 1 June showing that the ENSO index remains in a neutral phase, with a value 0.5°C above average. Seasonal forecast models point to a transition from neutral to El Niño conditions between June and July 2026, with an 82% probability. The phenomenon is expected to persist through the end of 2026, with a probability exceeding 90%. The IPMA expects a moderate-to-strong manifestation, amplified by the climate crisis, though it cautions that effects in Portugal are neither direct nor easily predictable.
A longer-term trend
Copernicus stressed that the May heatwave, while remarkable, fits within the broader pattern of rapid warming across Europe and a long-term trend toward heatwaves that are more frequent, more intense, and occurring earlier in the season. The institute's monthly global climate bulletin noted that extreme events are becoming the norm. The data underscores the sustained pressure on the climate system from the combustion of coal, oil and gas since the pre-industrial era.
