The Meteo-France weather service lifted its red warning but forecast a “very hot day” across a large central band of the country, with the mercury expected to rise to 42 degrees Celsius (108 degrees Fahrenheit) in some parts.
With France, Spain, Italy and parts of central Europe hard hit by all-time highest temperatures, officials pleaded with people to take precautions.
France's new record temperature of 45.9°C was registered on Friday in Gallargues-le-Montueux, a village in the southern department of Gard near Montpellier, breaking successive records set earlier in the day, Meteo-France told AFP.
This is the same area where the previous high of 44.1°C was set in August 2003 since records began at the turn of the 20th century.
The weather service said the new high was comparable to August temperatures in California's Death Valley.
Earlier Friday, the mercury rose above 44°C in the southeastern French town of Carpentras. The town was deserted, with cafe owners contemplating empty terraces which would normally be packed.
“We have never seen this!” one exclaimed.
France is just the seventh European country to register a plus 45-degree temperature, along with Bulgaria, Portugal, Italy, Spain, Greece and North Macedonia, Meteo France said.
Meteorologists blame a blast of hot air from northern Africa for the scorching early European summer, but the heat is due to die down from Sunday.
The heat has already claimed several lives, including a 17-year-old harvest worker in Spain and a 72-year-old homeless man in Italy.
Heat-related deaths have also been reported in Germany and France, mainly among the elderly.
France remains haunted by the memory of the devastating heatwave of August 2003 which exposed the shortcomings of emergency services at the height of the summer holidays and during which nearly 15,000 people were estimated to have died.
“I want to appeal to the sense of responsibility of citizens — there are avoidable deaths in every heatwave,” French Prime Minister Edouard Philippe said.
Public health warnings
After four people have also drowned in bathing accidents, Health Minister Agnes Buzyn lamented that despite a barrage of public health warnings, some parents were still leaving their children in hot cars and joggers were out exercising in the midday heat.
A Syrian child was seriously injured north of Paris Thursday after being catapulted into the air by water gushing from an open fire hydrant and then crashing to the ground.
The incident occurred in the multi-ethnic Saint-Denis neighbourhood where “uncapping” hydrants has long been used as a way to cool off.
Meanwhile, blazes have also ravaged more than 600 hectares of land and several homes in France.
The stifling temperatures have caused air quality to nosedive in some European cities, prompting local authorities to take anti-pollution measures.
In Paris, Lyon and Marseille, authorities have banned the most polluting cars from the roads in recent days.