Towards the earliest heat wave ever observed in France

Since the end of last week, a cold drop present on the Azores has brought up heat over Spain and Portugal. The depression is driving a southerly flow that sucks theair from North Africa to propel it towards Europe: this is the mechanism of heat pump. Morocco and Spain faced scorching temperatures last weekend, with up to 42°C in Seville, Andalusia. Highs of 45°C or even 46°C are possible in Morocco these days. In France, the heat has already started to increase in recent days, with 36 ° C recorded in Nîmes this Sunday, and 37 ° C recorded in Hérault and Vaucluse.

The heat peak is expected on Friday

This “heat feather”, as the meteorologists, will lead to an episode of very hot weather over almost all of France between Wednesday and Saturday. The hot air centered on Spain will rise towards our country, starting with the southwest on Tuesday, then towards the north on Wednesday and then the east. The heat peak will be reached between Thursday and Saturday, the hottest day being forecast for Friday, with temperatures exceeding the seasonal average by 10 to 15°C! The values ​​can go up to:

• 35/36°C in Paris (against a normal of 24°C);
• 40°C in Biarritz (against 23°C);
• 39/40°C in Toulouse (against 25°C);
• 30/32°C in Lille (against 21°C);
• 35°C in Perpignan (against 26°C);
• 36°C in Montélimar (against 26°C);
• 32°C in Brest (against 19°C).

Particularities of this exceptional episode, the heat will reach usually cooler areas such as Brittany (over 30°C over almost the entire region), monthly records may be broken and the official heat wave thresholds will be a priori exceeded in some departments.

Heatwave thresholds may never have been reached so soon

Meteo France defines a heatwave as ” an episode of high temperatures, day or night, over an extended period. As part of meteorological vigilance, account is taken of the exceptional nature of nighttime temperatures. When these are high for several consecutive days, the risk of mortality increases in frail people. Temperature thresholds diurnal nights are set for each region. The heat wave is therefore a question of temperatures but also of duration (more than three days). This week, several departments in the south-west should officially enter the heat wave thresholds, with temperatures exceeding 35°C during the day and 20°C at night: these thresholds will be reached for four to five days locally. On the northern half, the thresholds should not be reached for more than two days, even if uncertainty remains over the end of the period, linked to the arrival of storms over the weekend.

The heat waves affect France almost every summer, mainly between early July and mid-August, but they can sometimes occur outside this period. The appearance of heat waves in June is moreover a phenomenon that tends to occur more and more for 20 years. Weather report France specifies that France already experienced a heat wave in June 2017 remarkable for its precocity and intensity: since 1947, only the heat wave from June 18 to 28, 2005 had been so early and never had a day in June been so hot since the start of Météo-France readings ». Another more recent heat wave, end of June 2019which was marked by the day of June 27, the hottest day recorded in the month of June, with an average temperature in France of 27.9 ° C.

However, the last three major reference heat waves in June (2005, 2017 and 2019) occurred after June 18, that of 2022 starting on June 15 and ending, a priori June 18. If the heat forecasts continue to be confirmed, France could therefore experience its earliest heat wave ever observed since the start of weather records.