Some 4,000 French schools will remain closed on Friday or will host families escaping an unprecedented heatwave in the south of the country.
State weather service Meteo France declared its first-ever heatwave red alert, saying temperatures in some southern areas are set to reach 42 to 45 degrees celsius.
The cities of Marseille, Nimes, Montpellier and Avignon and the lower Rhone Valley are among the areas covered by the red alert.
On Thursday, Meteo France registered the country's highest-ever temperature for the month of June -- 42 degrees - in a village in the southern Ardeche department.
The heatwave was "exceptionally intense and exceptionally early," French Prime Minister Edouard Philippe said, calling on citizens to follow "their sense of responsibility."
"Heatwaves lead to avoidable deaths because the heat, the tension sometimes, makes people take risks," he warned, adding that the rate of drownings had risen to one per day.
Motorway operators have been instructed to distribute water and to provide advice to travellers in French and English for the sake of tourists, Philippe added.
French authorities have planned carefully for hot weather since a 2003 heatwave that led to 15,000 deaths in the country and an estimated 70,000 across Europe.
Australian Associated Press