HEAT 2023. France has had a series of heat waves and heat waves in recent years. Should we expect the same scenario in this summer of 2023? Here are the first forecasts for the summer.
[Mis à jour le 2 juin 2023 à 18h00] Will the summer of 2023 be marked by new heat waves and heat waves? The first forecasts for the summer have fallen and already indicate expected peaks with very high temperatures. At the beginning of June, temperatures jumped with the barrier of 30 degrees approached or announced, for example in Paris, Bordeaux or Toulouse. Is this a heat wave? No, if we rely on the very definition of this meteorological episode.
What is a heatwave?
As a reminder, we speak of a heat wave when these four characteristics are combined:
What are the recommendations to follow during the heat wave?
Heat wave, heat peak, heat wave and heat dome: what are the differences?
Heat wave and heat wave are two different things. To speak of a heat wave, the temperatures must be five degrees higher than normal for the season, day and night, and this for at least three days and three nights. The heat wave temperature threshold therefore differs according to the departments and regions. Heat waves most often occur in France in July and August. We must be vigilant from the month of June. High temperatures, even above seasonal norms, do not necessarily mean a heat wave. Most often, these are heat waves.
The term heat peak is more to be used during a sudden rise in temperature, whereas a heat wave corresponds to a longer episode. Météo France judges that a heat wave is in progress when temperatures above the monthly average are detected by more than three degrees Celsius, for at least three days.
Finally, heat dome is another term used. It settled over almost all of France in May 2022. This meteorological phenomenon is explained by a large mass of hot air from Morocco and Spain, trapped by atmospheric pressure. This usually occurs in summer, but also in spring. It results in scorching heat.
Météo France provides several levels of heat wave vigilance: level 1 (green) corresponds to a “seasonal watch”, level 2 (yellow) to a “heat warning” and it is level 3 (orange) which corresponds to “the ‘heat wave alert’. Finally, level 4 (red), the highest, determines “maximum mobilization”. In summer, it is not uncommon for several departments to be placed on orange or red alert for the heat wave.
Heat wave: what are the temperature records recorded in recent years?
If the heat wave of the summer of 2003 remains in everyone’s memory (and that of 1976 also among the old), France has since experienced other episodes of very hot weather. In summer 2019, several absolute temperature records were reached in different cities. According to data from Météo France, 50 cities had thus recorded a new record since July 25, 2019. While the summer of 2019 had been very hot, some records were broken during the heat wave of mid-June 2022. During the day heat wave of Saturday June 18, 2022: 150 municipalities broke a heat record, according to meteorologist Patrick Marlière, interviewed by BFM TV: “We went from 70 cities with broken monthly records, to more than 150 today in France, from the Pyrenees to the Belgian border”. The city of Nantes thus broke its record for the month of June with 39.1°C. In the South-West, records at more than 40 degrees have been reached: Biarritz with 42.9°, Saint-Jean-de-Luz with 42° or Bordeaux with 40°.
The July 2022 heat wave also set temperature records on Monday July 18. Of the 63 records recorded that day, the majority are in the north, west or southwest. We can cite :
- Beaulieu-sur-Layon (49): 42.7°C
- Biscarrosse (40): 42.6°C
- Nantes (44): 42°C
- La Roche-sur-Yon (85): 41.5°C
- Cholet (49): 41.3°C
- Niort (79): 41°C
- Rennes (35): 40.5°C
- Caen (14): 40.1°C
- Dinard (35): 40°C
- Saint-Brieuc (22): 39.7°C
- Noirmoutier (85): 38.7°C
- Lorient (56): 37.6°C
- Brest (29): 39.3
- The island of Yeu (85): 35.9°C