Highs of 40C possible as France braces for September heatwave

Updated forecasts predict temperatures of potentially 40C in southern France at the end of this week, matching previous September records. 

Forecasters initially pointed to a new spell of hot weather in the south, with temperatures set to reach 35C. 

However, new models now suggest temperatures may reach even higher, particularly in the south-west and western Mediterranean. 

Temperatures of 40C are possible across much of the south-west between Friday and Sunday (September 4 - 6), with models closer to the time giving more accurate predictions of exact locations that will see the warmest weather.

The updated predictions were relayed by François Gourand, meteorologist with state forecaster Météo France, who also predicted temperatures of around 30C in Paris before the end of the week.

“For September, that is quite remarkable," he said to media outlet 20 Minutes, but it will not be "comparable to the heatwaves we experienced this summer."

“Temperatures will likely break records for the month of September,” in many southern areas, he added, including Nouvelle-Aquitaine, Occitanie, the Rhône Valley and some Alpine towns at lower altitudes. 

Heat records may be broken

Further north however, records set in the September 2023 heatwave are likely to remain in place.

This included highs of around 35C in Paris, Rennes, and Orléans, and 39C in Montmorillon and La Trimouille (Vienne).

The all-time national record for September is 40C, recorded in Corsica in 1975.

Intense heat this week will be less impactful in the northern half of France, with Paris the only area expected to see thermometers hit 30C or above before the weekend. 

On Sunday, highs of 30C are possible in Brittany and areas south of Paris, but this remains uncertain.

North of the Seine, temperatures will only be a couple of degrees above average, although Sunday may see temperatures of 27C across regions including Normandy and Hauts-de-France.

The spike in hot weather could cause monthly records for September to be surpassed, if temperatures remain above average for a considerable period (even without hitting heatwave thresholds). 

The 2023 September heatwave contributed to an all-time monthly average high of 21C, and with temperatures across all of France set to be well above this for at least the next week, it is possible the recent record will once again be broken.

Heatwave warnings already set for Thursday

Temperatures begin to climb significantly today in the Languedoc area, followed by a wider increase in temperatures across the south tomorrow. 

This headstart will see two departments – Hérault and Gard – placed on a heightened tier-two alert for heatwave conditions (canicule) by Thursday. 

As temperatures continue to rise across the south – temperatures may peak on Friday but intense warm conditions are likely to be in place until at least the end of the weekend – heightened alerts are likely. 

The issuing of heightened tier-three orange warnings will coincide with heatwave plans being raised in relevant departments, with extra resources given to help vulnerable residents.

This includes checking up on people included in the local ‘heatwave register’.