French weather forecaster Météo France on Friday upgraded the orange weather warning to red for northern parts of the country as temperatures reached 37C. The red warning means a potential danger to life or health.
Placed on a red warning were Paris and the départements of Essonne, Hauts-de-Seine, Seine-Saint-Denis, Val-d'Oise, Val-de-Marne and Yvelines.
The départements of Eure and Seine-Maritime in Normandy were also put on red alert.
Another 53 départements remain on orange alert for the heatwave, which is forecast to last well into next week.
Highs of 42C are forecast in some areas while on Friday afternoon the majority of the country was 35C or hotter, said Météo France.
At 3.30pm on Friday temperatures of above 38C were recorded across southern France and Val-de-Loire, including 40.2C at Bretenoux in the Lot département and 40.4C in Barbezieux in Charente.
Cities including Paris have activated their hot weather plans which involve the opening of 'cool rooms' in the city and the free distribution of fans to vulnerable people.
However health minister Olivier Véran has warned that people in France need to continue to wear masks, despite the heat.