As of 5:00 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.
Sights in the French capital Paris have also been impacted by the hot weather.
The world’s most visited museum, the Louvre, said it was bringing forward its closing time from Wednesday to Saturday from 18:00 to 16:00 local time.
The Louvre said its historic building “remains fragile, external and is not sufficiently adapted to climate change”, adding that the “build-up of heat is at its highest at the end of the day, and intensified by the volume of visitors”.
In France, among those who died in heatwave-related incidents was a 13-year-old girl who had gone for a dip with her family in the River Seine at Fontaine-La Port on Sunday evening, although she did not know how to swim.
Several drownings have also been reported in Germany.
While Spain has experienced baking heat over the last few days, temperatures are expected to start falling on the Iberian peninsula on Wednesday.
But red heat alerts remain in place for parts of northern Spain, with a maximum temperature of 42C possible in parts of the Basque country, forecaster Aemet said.
In Italy, meanwhile, 16 provincial capitals are now under red heat alerts, with Latina added to the list on Wednesday, while Bari will be added on Thursday, Italian news agency Ansa said.
