A powerful heat wave has swept across western Europe, shattering temperature records for the month of May in the United Kingdom, France and Spain, with forecasters warning the extreme conditions will persist through the end of the week. The event is being driven by a "heat dome" — a mass of hot air originating from northern Africa and Morocco that has become trapped under a high-pressure system over western Europe, pushing temperatures 12 to 13 degrees Celsius above seasonal norms.

The United Kingdom recorded its hottest May temperature since records began when the mercury reached 34.8°C at Kew Gardens in southwest London, more than two degrees above the previous record. Across the Channel, France's national weather agency Météo-France reported that over 350 weather stations — mainly in the west of the country — logged their highest-ever May temperatures, with a peak of 37.1°C recorded near Hossegor in the southwestern Landes department. The national temperature average hit a record 24.4°C on Monday. Thirty-one of metropolitan France's 96 administrative departments were placed on heat alert, the first time the country's warning system, introduced in 2004, has been activated in May. In Spain, temperatures in southern areas have already reached 38°C, and forecasters warn that parts of the Guadiana, Guadalquivir and Ebro valleys could approach 40°C by Thursday or Friday, with widespread "tropical nights" — where temperatures remain above 20°C after dark — expected in the southwest.

The heat has turned deadly. A 53-year-old man died of an apparent heart attack during a 10-kilometre running race in Paris on Sunday, while ten other runners required emergency hospital treatment in the capital's suburbs. In the eastern Rhône region, a 28-year-old woman died of heatstroke at an indoor athletics meeting. France's sports minister, Marina Ferrari, cautioned that "practicing sports in extreme heat requires absolute vigilance." In response, Italy's Lazio region — which includes Rome — brought forward outdoor work restrictions, limiting labour with prolonged sun exposure between noon and 4pm, measures that previously had not taken effect until late May.

Climate scientists are unequivocal about the broader context. "This is an unprecedented event with a one in 1,000 chance of happening at this time of year based on the climate from 1979 to 2025, and virtually impossible in the preindustrial era," climate scientist Christophe Cassou told Le Monde. Météo-France warned that such events will "occur more and more often and earlier and earlier." Climate researcher Robert Vautard noted that the extension of the heat wave season is "entirely characteristic of the effects of climate change," adding that similar extreme heat events in April and October may eventually become a reality. The UK's Met Office described the record temperatures as "a good indication of climate change in action."

The heat wave matters beyond the immediate health risks. It arrives weeks before summer officially begins and tests infrastructure — from hospitals to transport networks — that was not designed for such conditions. UK climate advisers last week warned the government that the country was "built for a climate that no longer exists." With climate models suggesting that June-level heat waves are now roughly ten times more likely in Europe than in the preindustrial era, and the same trajectory emerging for May, this week's records may signal what forecasters describe as an accelerating shift in what Europeans should expect every spring.