As of 05:00 local time, La Rochelle in the southwest had already recorded a temperature of 29C, the forecaster said, with a high of 43C possible later in the day in the region.
Highs of 39 to 40C are forecast across much of the country’s west, from Paris to Brittany, and are expected to remain the same until the weekend.
Temperatures peaked on Tuesday, with a high of 44.3C recorded in parts of Landes, in the southwest.
Some relief from the heat is expected from Friday, with temperatures forecast to gradually drop over the weekend. This change will come with thunderstorms, bringing a risk of flash flooding and large hail.
Speaking to French radio, labour minister Jean-Pierre Farandou said “we’re in the process of finding out we’ve become a hot country”.
The heat caused the first major power outage in the country, with around 68,000 homes left without power in the north-western Finistère region on Tuesday evening due to a problem with a transformer, authorities said. Power is not expected to be restored for everyone until the end of Wednesday at the earliest.
Elsewhere in the Maine and Loire region, more than 150 firefighters were deployed to fight a major fire on Tuesday in the Breignon forest in Saint-Macaire-du-Bois. It was brought under control overnight, authorities said.
