The French weather service, Météo-France, has issued a red alert for Tuesday for sixteen departments, including areas around the capital, Paris.
The entire French territory is experiencing a heatwave, but the heat will be particularly intense in the Paris Region on Tuesday and into the night.
The last time a red alert was declared in France was in August 2023.
Another 68 departments are on orange alert for Tuesday, the second-highest alert level.
On Monday, 84 of France's 96 mainland regions were under an orange alert. This was an "unprecedented" situation, according to Climate Minister Agnès Pannier-Runacher.
Heat warnings are also in place for parts of Germany, Italy, Portugal, Spain and the UK, as well as Croatia and other countries in the Balkans.
