Heatwave alert raised for south of France - how hot will it be?

An official heatwave (canicule) warning is being issued for the south-east of France tomorrow (July 26), mainly due to high temperatures overnight Friday to Saturday.

The tier-two yellow warning – the first of three levels of heatwave alert levels – will come into force in the Alpes-Maritimes, including Nice, and Haute-Corse departments from 18:00. 

Météo France only provides official warnings up to 48 hours in advance, so it is currently unknown how long it will remain in place for.

With temperatures remaining stable, it is likely to last throughout the weekend and possibly into next week. 

How hot will it be? 

Surprisingly, though, the Alpes-Maritimes will not be the warmest place in France tomorrow (July 26) and at the weekend.

Highs of 30C are forecast in Nice, although in direct sunlight, this may be closer to 40C (officially recorded temperatures are taken in the shade). 

By comparison, parts of inland Provence will see highs of 35C (in the shade) and early next week, temperatures of 40C or higher may hit the south-west. 

The specific alert being raised is not for a vague de chaleur, when temperatures are excessively high in the daytime, but for a canicule. 

Canicule warnings take into consideration both daytime and evening temperatures, which usually drop significantly and allow cool air to freshen areas facing high heats. 

If evening temperatures remain high, canicule warnings are raised, as they do not allow buildings – and people – to naturally cool down.

Météo France predicts that for a number of days, temperatures around Nice will barely drop below 27C (room temperature) making it difficult or even impossible for homes to cool down overnight without the use of fans or air conditioning. 

In comparison, the areas of Provence facing daytime highs of 35C will see temperatures drop to around 18C – or even lower – overnight. 

Canicule and vague de chaleur warnings are based on regular local temperatures – for example, the highs required for a warning to be put in place in Normandy are significantly lower than around the Mediterranean, where temperatures are higher and infrastructure is built with the purpose of keeping homes and people cool.

Read more: What are the different heatwave warnings in France?

Aside from using fans and air conditioning, other tips to keep you home cool include keeping windows and shutters closed to prevent direct sunlight heating up rooms, as well as keeping doors open to circulate air in your property. 

On a personal level, drinking water regularly, cutting down on alcohol consumption and eating cooler, healthier foods, is also recommended. 

Read more: How to keep your house cool in the high heat of the French summer

Read more: France heatwave tips: How to sleep, keep cool and stay healthy

The first week of August is set to see very high daytime temperatures in the south-east (early forecasts for the area are highs of 35C in the shade in Nice, up to 44C in direct sunlight) combined with overnight temperatures of around 26C. 

This could lead to more canicule warnings and possibly at a higher level. 

As heatwave warnings increase, local authorities have access to a wider range of measures set to limit the impact of the warm weather, particularly for the elderly and other vulnerable people.

Read more: What action is advised with different Météo France weather warnings