A swathe of south-eastern France around the cities of Lyon and Grenoble was on heatwave alert on Monday as forecasters warned of high temperatures made worse by humidity.
French weather service Météo France has placed five departments on orange alert, the level below its maximum heatwave warning.
Savoie and Haute-Savoie, on the border with Switzerland, were added to the alert from Monday.
The Ain and Isère departments have been on heatwave watch since Sunday, and Rhône – the department around Lyon, France's third-biggest city – since Saturday.
Temperatures will remain persistently high in the region throughout this week, Météo France said.
#canicule
— VigiMétéoFrance (@VigiMeteoFrance) August 13, 2023
Lundi ce sont désormais 5 départements qui seront concernés par la #VigilanceOrange, avec l'ajout des départements de la Savoie et de la Haute-Savoie. Les températures vont rester durablement élevées sur Rhône-Alpes toute la semaine prochaine.👇https://t.co/wsrtEYFflV pic.twitter.com/4KCNPF83z9
Another four nearby departments – Loire, Haute-Loire, Ardèche and Drôme – were on the lower yellow alert for shorter hot spells.
The weather service has forecast temperatures of between 34 and 36 degrees Celsius in the worst affected areas, though it warns they might top that in some spots.
Storms in the Rhône area will also raise the humidity, making the heat feel more intense.
Météo France is predicting even higher temperatures on Monday in the Pyrénées-Orientales department on the border with Spain, where a hot southerly wind over the mountains is forecast to bring spikes of up to 39 degrees Celsius
But the heat there is expected to break from Tuesday.
While temperatures have been below average in much of France for the past month, the second half of August is expected to bring the hottest period of the summer.
Meanwhile the weather service issued a storm warning for five departments in the south-west, where it said there was a risk of heavy rain, hailstorms and strong winds on Monday night.
