As of 05:00 local time, La Rochelle recorded 29°C, with potential highs of 43°C later that day.
Western France, including Paris and Brittany, faces sustained temperatures of 39–40°C until the weekend.
Tuesday saw extreme heat, peaking at 44.3°C in southwestern Landes.
Relief begins Friday as temperatures gradually decrease, accompanied by thunderstorms that may cause flash flooding and large hail.
Labour minister Jean-Pierre Farandou noted France’s escalating heat challenges during a radio address.
A major power outage affected 68,000 homes in Finistère due to a transformer failure on Tuesday evening, with full restoration expected by Wednesday’s end.
In the Maine and Loire region, 150 firefighters controlled a significant forest fire in Saint-Macaire-du-Bois by Tuesday night.