France weather agency Météo France issued an orange alert for 14 départements of France on Tuesday afternoon, including the Paris region.
Orange is the second highest level of alert in France and urges the public to be vigilant and to avoid unnecessary travel.
The other départements to get weather warnings were Aisne, Ardennes, Aube, Marne, Nord and Yonne (see map below).
The agency said that even healthy people will be at risk if they're in the areas with orange alerts, and it urged people to watch out for signs of heat stroke, especially among the sick and elderly.
Earlier in the morning, the agency issued yellow heatwave warnings for 36 of France's 101 départements, but increased the total to 48 in the afternoon (see map above).
"After cooler air last week, the thermometer is going to continue its roller coaster ride that started in July," agency forecaster Sébastien Léas told Le Parisien newspaper.
Tuesday afternoon in France and not a cloud in sight. Photo: Météo France
Over the next two days the rising temperatures will generally continue, the agency noted, and the heatwave alerts have been put in place until Thursday morning.
Due to the longer nights of late August, however, temperatures are expected to duck below 20C during the evenings, providing some welcome relief for light sleepers.