The fire broke out alongside a highway near Fontainebleau, home to one of France's best-known royal palaces, which once served as a hunting lodge and autumn residence for past monarchs.
By midnight, the flames had scorched more than 800 hectares, fanned by hot winds.
Just 70 kilometres from Paris, the blaze forced the closure of the A6 highway linking Paris with Lyon and the south. Smaller fires in the area also disrupted high-speed train services.
"The fight continues today," the French fire service said on X.
Local residents have been warned that the Canadair planes will have to scoop water from the river Seine, which flows through central Paris.
European countries are worried about increasingly frequent heatwaves and record-breaking temperatures. Most scientists say the fires are driven by climate change, with large swathes of continental Europe parched.
Wildfires have already ripped through regions of France, Spain, Portugal and Greece, charring thousands of hectares of land.
The death toll from a blaze that swept through Spain's southeastern Almeria province rose to 13 over the weekend, when a 93-year-old British woman died of burns.
Western Europe is gripped by its third prolonged spell of baking temperatures this summer.
A heatwave in late June likely killed thousands of people, with countries reporting more than 10,000 excess deaths. Power supplies were disrupted, schools shut and temperature records broken in France, Spain and Britain.
"To have this kind of excess at this time of year is unusual. It's really high," said Lasse Vestergaard, chief physician at Denmark's Statens Serum Institut, which hosts EuroMOMO, a Europe-wide mortality surveillance system.
"It is difficult to explain this high excess mortality by anything but the extreme heat," Vestergaard told Reuters.
