Eight consecutive days above 32°C in Paris. Only three times in recorded history has the French capital seen such a streak — and all of those were in the depths of summer. This one arrived in May.

France is in the grip of what Météo-France calls an “unprecedented, historic, exceptional” heat episode. On Tuesday, May 26, the national average temperature reached 24.9°C, the hottest May day ever recorded in the country, surpassing a record set just one day earlier, according to provisional readings. Temperatures across much of France have climbed nearly 15°C above historical norms for late May.

Angoulême hit 37.8°C on Thursday — the highest May temperature ever measured in France. Brest, the Breton coastal city more associated with grey skies, recorded four straight days above 30°C, something seen only twice in 80 years, both times in midsummer. More than 350 weather stations logged new monthly records on Monday alone. Nighttime offered no relief: in Calais, the mercury never dipped below 19.1°C, a May record for the station.

The cause is a heat dome — hot air from Morocco trapped under a high-pressure system over Western Europe. Météo-France activated its national heat warning system for the first time in May since its introduction in 2004, with 13 departments placed on orange alert.

Climate scientist Christophe Cassou told Le Monde the event had a one-in-1,000 chance of occurring at this time of year in the current climate, and would have been “virtually impossible in the preindustrial era.” Robert Vautard, a climate researcher, told Agence France-Presse that the extension of the heat wave season into May is “entirely characteristic of the effects of climate change.”

Seven deaths in France have been linked to the heat, including drownings and fatalities during sporting events. The episode is expected to ease from Sunday as storms arrive from the west.

Sources