France's traffic authorities said the peak was reached just after noon, easily beating both last Saturday's record of 760 kilometres (470 miles) and the previous record of 762 kilometres set on August 3 of last year.
The country has been sweltering through a heatwave since Thursday, with temperatures pushing towards 40 degrees Celsius (104 Fahrenheit) in several areas.
In the southwest, Brive-la-Gaillarde broke its record with 40.8C on Friday, as did Cognac with 39.8C, while Nantes in the west posted a new record of 39.6C.
No relief is expected until Wednesday, with the soaring temperatures compounding the pressure as the country's coronavirus outbreak worsens, the number of daily infections hitting 2,288 on Friday.
Authorities reminded sweltering citizens that masks must continue to be worn where they have been mandated, despite the heat.
Roland and Helene, retirees in suburban Paris, said they go out in the morning “to get some fresh air,” but then spend the rest of the day hiding in their apartment. “We fear the heat a lot,” Helene said.
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.
Last year was France's hottest on record, and the Meteo France weather agency has warned that global warming could double the number of heatwaves by 2050.