A new heatwave on Sunday hit much of southern and eastern France as authorities warned of an increasing risks of wildfires and some cities granted free access to swimming pools.
Unusually high temperatures, described by national weather service Meteo France as "particularly late for the season", are expected to persist throughout the week.
"We expect 38°C to 39°C in the region of Toulouse and up to 40°C and 41°C in the lower Rhone valley, between Montelimar, Nimes and Carpentras," Meteo France said.
The latest wave of hot weather has been caused by a so-called heat dome, a meteorological event characterised by a persistent high-pressure system that acts as a barrier, trapping warm air on the ground.
The government on Saturday closed off access to areas deemed to be at high risk of forest fires including the Esterel Massif on the Mediterranean coast near Nice.
Eastern France experienced a heatwave early last month, while another spread across the Mediterranean region and southern France later in July.
Experts say global warming is to blame for an increase in the frequency in heatwaves, which rarely occur in France after August 15.
Meteo France said only six heatwaves have been recorded in France since 1947 at this time of year: in 2001, 2009, 2011, 2012, 2016 and 2017.
Records were reached on August 18 and 19, 2012, when temperatures reached 41.5°C in eastern France but such extreme weather events are now expected more often.
Between 1950 and 1999, temperatures exceeded 40°C in late August on average 0.8 times a year, but this has happened more than 13 times annually since 2000.
"The 2020 decade has already outpaced preceding ones, despite only three years having passed (2020, 2021, and 2022)," said Meteo France.
The heat has prompted some authorities to set up cooling systems for the public.
The south-eastern city of Grenoble has installed six mist sprayers and media outlets have published a list of air-conditioned buildings that are free to enter, including museums and libraries.
The mayor of France's second-largest city, Marseille, said on social media platform X, formerly Twitter, that swimming pools would be free from Sunday to Wednesday.
"In this period of very high heat, every gesture counts to protect ourselves," Benoit Payan wrote. Free access to swimming pools also featured during last month's heatwave.
The city has extended opening hours of parks and beaches.
Local newspaper La Provence reported that municipal humanitarian emergency service Samu Social was distributing water bottles, hats, sandals and maps of the city's fountains.