Is this heat wave exceptional?

The archives of the meteorology show that France has experienced many heat wave episodes, durations and of different intensities depending on the year. The mid-June 202 heat wave2 was marked by its precocity, never such intense heat had affected our country before June 18, since the beginning of the weather reports. The July 2022 heatwave is, for its part, more violent in the west and more durable. July is the month par excellence for heat waves and often marks theapogee of the heat in France, but, for all that, never had such high temperatures been reached before in the west and north-west of our country: 39.3°C in Brest on the tip of Finistère on Monday July 18, and at our British neighbours, more than 40°C in London this Tuesday, July 19.

Twenty absolute records in France were broken on Monday July 18: this means that it had never been so hot in all months since the start of weather records, most of which are 50 to 70 years old. About 13% of official French weather stations were affected by absolute records on Monday July 18, that is more than one in ten!

In the South, the heat is classic throughout the summer, but not at such high levels, and as repetitively as in recent weeks, as detailed Weather Languedoc organization : “ In the hinterland of Languedoc, the average maximum temperature has exceeded 36°C at certain stations since 1^er July. The norm is not 40°C in summer. It is only 31°C in Nîmes or 29.3°C in Montpellier-Fréjorgues. We explode the standards, so often ”.

The heat wave of August 2003 remains, despite everything, the most intense ever observed in France: from August 1 to 15, 2003, constant high temperatures affected the whole of France, claiming 15,000 to 20,000 victims in our country. Its duration was unmatched to date (16 days), but even more extreme temperatures were recorded in June 2019during a much shorter, but even more intense heat wave: it was precisely on June 28, 2019 that the absolute heat record in France was recorded: 46°C in Vérargues in Héraulta value much higher than the maximum temperatures recorded during June and July 2022.

In July 2006, a particularly long heat wave (18 days), but less intense and more restricted, affected the Rhône Valley. Compared to the heat waves of the past twenty years, the July 2022 heat wave is therefore particularly long-lasting (10 to 14 days), widespread and intense. This is one of the longest heat waves that France has known, with many absolute records, without beating that of 2019.

Take into account weather readings, not memories or feelings

But what about the big ones waves heat from the past? The year 1976 remains in the memories of many French people. That year, persistent anticyclones blocked the precipitation almost permanently from April to July 1976: fine, dry and lasting weather imposed itself on France, with strong heat. But the year 1976 remains remarkable for its drought above all, and not for its temperatures: 40°C in Arcachon, 38°C in Bordeaux and 34°C in London. Remarkable values, but which do not reach the 46°C in the Hérault recorded in 2019, nor the 42°C recorded in Nantes or the 39.3°C in Brest on July 18, 2022.

The summer of 1947 was one of a series of scorching summers that affected western Western Europe between 1945 and 1952. June, July and August 1947 were marked by excessive heat, with 40 °C in the Paris region and 34°C in London. Many of the extreme temperatures recorded in 1947 were not finally beaten until more than 50 years later, during the heat wave of 2003, which were then sometimes beaten in 2019, then in 2022.

Another great heat wave, that of 1911, whose duration is not well defined, for lack of official weather records: from July to September, temperatures often reached 35 to 40 ° C in many regions of France, killing 46,000 people. . Further afield, historical records show devastating heat waves in 1718 and 1719, killing hundreds of thousands. However, it is not possible to compare the weather events before 1947 to those of our modern era, since there were no reliable and official weather records before that year!

Historical writings are therefore to be taken with great caution because they very often transcribe personal feelings: heat with certainty, but it is not really possible to know at what level. It must also be taken into account that the slightest heat wave was in the past, before the 1950s, devastating and deadly due to the majority of the population working outside, or in factories.

Finally, while memories are often biased, official measures of Meteo France are the only reliable values ​​to take into account. The heat wave is not a new phenomenon in our country, but the July 2022 weather readings are clearly exceptional in general, and unprecedented for some. Global warming undeniably results in more frequent heat waves, with more extreme values ​​repeatedly, if we are to believe the official weather records… and not memory or personal feelings.