May 2026 was the second warmest May on record globally, according to the Copernicus Climate Change Service.
The global average surface air temperature was 15.81°C, 1.42°C above the pre-industrial average.
Sea surface temperatures between 60°S and 60°N were also the second highest on record, behind May 2024.
Exceptionally warm waters in the Equatorial Pacific pointed to a developing El Niño, with WMO giving an 80% chance of formation between June and August.
Europe saw an early and intense heatwave, with May temperature records broken in France, the UK, Ireland and Portugal.
Large parts of Europe, central Asia, Madagascar, south-west Australia and South America were drier than normal during the month.
May 2026 was the second warmest May on record, with early and intense heatwaves in many parts of Europe and record-breaking temperatures in the tropical Pacific Ocean hinting at the coming El Niño event, according to the latest update from the Copernicus Climate Change Service, (C3S), of the European Centre for Medium-Range Weather Forecasts.
The global average surface air temperature for May 2026 was 15.81 degrees Celsius (°C), which was 0.55°C above the 1991-2020 average and 1.42°C above the pre-industrial average for 1850-1900. The anomalies were second only to May 2024.
Sea surface temperatures, or SSTs, between the latitudes 60S and 60N were also the second highest on record, according to C3S, behind May 2024.
With the El Niño phenomenon developing in the Equatorial Pacific Ocean, SSTs were at “exceptionally high levels” across large parts of the region. There is an 80 per cent chance of El Niño developing in the region between June and August, according to the World Meteorological Organization (WMO).
In Europe, May was marked by a sudden switch from colder-than-average temperatures to warmer-than-average temperatures around 20 May. Several May temperature records were broken across France, the United Kingdom, Ireland and Portugal during an early and intense heatwave.
The “feels-like” temperatures over the region were in the range of 35°C to 40°C in many places. This translated to “strong”, above 32°C, and “very strong” heat-stress conditions, according to C3S. Temperatures were far above normal during both day and night.
“The rapid transition likely increased impacts on populations, leaving little time for people — or crops and ecosystems during growing season — to acclimatise to much higher temperatures,” C3S said in a press statement.
The heatwave occurred because of a powerful heat dome over the region at the time. Such heatwaves are being made hotter, longer and more frequent by a warming planet and the changes it is driving.
Large parts of central and western Europe, as well as some parts of eastern Europe, experienced drier-than-average conditions in May 2026. This included places such as Italy and southern Spain, and was partly aided by the heat dome and extreme temperatures.
River flows in May were below average in central, eastern and north-eastern Europe, mainly because of below-normal rainfall. In the Fennoscandia region, including Finland, very low river flows were mainly due to low snow cover.
Overall, the spring season was also drier than average for most of Europe, with river flows in important catchments such as the Danube, Vistula and Baltic Sea assessed as below average.
Apart from Europe, many other regions were also drier than normal in May 2026. These included central United States, central Asia, Madagascar, south-west Australia and many parts of South America. For many of these regions, including Madagascar and south-west Australia, the entire spring season was drier than normal.
“May 2026 was the second warmest May on record globally, extending the exceptional global warmth, with near-record temperatures in both the atmosphere and the ocean,” said Samantha Burgess, Strategic Lead for Climate at ECMWF, in a statement from C3S. “In Europe, an unusually early and intense heatwave demonstrates how quickly climate extremes are becoming the new normal rather than the exception.”
The hot and dry month of May in many regions around the world points to the development of El Niño conditions in the Equatorial Pacific Ocean, as indicated by C3S.