Météo France, the country's national weather agency, said on Wednesday that we could be heading towards a second heatwave, but that forecasts were not yet definitive.
The agency said it would continue to monitor weather changes and patterns, which are constantly evolving, over the coming days.
A heatwave is classified as multiple days with abnormally high temperatures.
The agency warned that mercury would begin to climb this weekend in France and most places would likely hit 35C by next Tuesday, with the exception of the littoral Atlantic and north-west regions.
Wednesday and Thursday will likely see peak temperatures reach as high as 39C-40C in the south-east and 35C in Nouvelle-Aquitaine.
At the end of next week, some thunderstorms are expected to break out on the main mountainous massifs of France, but it is unlikely that they will extend to the plains. While this might cool things down, the overall temperatures are not likely to fall below 30C
Night temperatures in most areas, with the exception of the Rhône-Alpes and Provence-Alpes-Côte d'Azur regions, are likely to drop below 25C-27C.