Prime Minister Elisabeth Borne's office has set up a crisis team to tackle a drought that has forced scores of villages to rely on water deliveries by truck, prompted state-run utility EDF to curb nuclear power output and stressed crops.

Temperatures were expected to hit 37 Celsius in the southwest on Sunday before the baking hot air spreads north early in the week.

"This new heatwave is likely to set in," La Chaine Meteo, similar to the US cable service The Weather Channel, said.

National weather agency Meteo France said it was the worst drought since records began in 1958 and that the drought was expected to worsen until at least the middle of the month. On average, less than 1cm of rain fell across France in July.

The corn harvest is expected to be 18.5 per cent lower this year compared with 2021, the agriculture ministry has said, just as Europeans contend with higher food prices as a result of lower-than-normal grain exports from Russia and Ukraine.

Meanwhile, a shortage of fodder because of the drought meant there could be a shortage of milk in the months ahead, the National Federation of Farmers' Unions said.

Nuclear operator EDF last week reduced its power output at a plant in southwestern France due to high river temperatures on the Garonne, and it has issued rolling warnings for reactors along the Rhone river.

The hot weather has compounded the utility's problems, with corrosion problems and extended maintenance at half of its 56 reactors reducing capacity as Europe faces an energy crunch.

Water restrictions are in place across almost all of mainland France to conserve water, including in many places hosepipe and irrigation bans.

Australian Associated Press