How has the climate evolved in France over the last 10 years? 16/11/2022

The new climatic conditions published this year reveal some changes in the French climate. While temperatures are rising predictably, rainfall and sunshine are also changing.

Strong heat most common

Temperatures increased by 0.42°C in France between 1981-2010 and 1991-2020. However, there are regional disparities. With +0.35°C, Brittany is the region that has warmed up the least. On the contrary, it is the Grand-Est that recorded the greatest increase with +0.50°C. Also, spring and summer are the warmest seasons. In spring, the south and east of France experience the most marked warming. In summer, it is in the east of the country that the increase is strongest (+0.7°C in Lyon and +0.67°C in Nancy) while it is much more contained in Brittany (+0.17°C in Brest).

Temperature increase by season and region between 1981-2010 and 1991-2020 – via Meteo France

With this significant increase in summer temperatures, the number of very hot days (at least 30°C) is increasing across the country. Between the periods 1981-2010 and 1991-2020, the increase is often 3 to 5 days per year in southern and central France. In Strasbourg and Dijon, we experience 14 to 18 days of intense heat. The increase is even greater between the Rhone Valley and the Mediterranean. Lyon won 6 days of intense heat (31 against 24). The most spectacular increase is recorded in Marseille-Marignane with 51 days of intense heat per year in the period 1991-2020 compared to 41 in the period 1981-2010, i.e. a 10-day increase ! It should be noted that this increase is much more limited going towards the English Channel and the Atlantic.

Evolution of the number of hot days (>30°C) per year between the periods 1981-2010 and 1991-2020 – Weather cities

Scarce frosts

In addition to intensely hot days, the decrease in the annual number of freezing days is an indicator of global warming. This average number is decreasing across France between 1981-2010 and 1991-2020. Some cities go as far as lose 8 days of frost per year between these two periods. This is the case of Lyon (which goes from 50 to 42 days) or Troyes (which goes from 70 to 62 days)! On its urban heat island, Paris experiences only an average of 21 days of frost per year.

Evolution of the number of freezing days (<0°C) per year between the periods 1981-2010 and 1991-2020 – Weather cities

Let us not forget that these values ​​are flattened over the period 1991-2020 and would be even lower if we did not take into account that the last decade was by far the warmest. For example, Paris experienced an average of 21 days of frost per year during the period 1991-2020, but this average drops to just 15 days if only the decade 2011-2020 is taken into account.

Variable rain

On average, the same amount of rain falls in France in the period 1991-2020 as in the period 1981-2010. However, there are seasonal and regional disparities. It is spring that dries the most in France, especially in the north and east. Summer gets wetter in the northwest (particularly in Brittany) while autumn is always wetter in the southeast (particularly in PACA). Throughout the year, the Grand-Est dries the most with a noticeable drop in 3.63% rains ! In contrast, PACA with +2.92% and Corsica with +4% they are the regions that see the greatest increase in their annual rainfall.

Precipitation evolution by season and region between 1981-2010 and 1991-2020 – via Meteo France

Can we say that it rains less than before? This is only true in some regions. Between the center and the northeastern district of France, the number of rainy days per year (at least 1mm) went back 2-5 days between the period 1991-2020 and the period 1981-2010, which is not negligible. Going from 123 to 118 days, Metz saw its annual number of rainy days decrease by 5 days between 1981-2010 and 1991-2020! Besançon recorded the same decline, going from 141 to 136 days. On the other hand, in the rest of France the number of rainy days per year varies very little. Cities like Lille, Brest, Nantes and Nice even won a rainy day between these two periods.

Evolution of the number of rainy days (at least 1 mm) per year between the periods 1981-2010 and 1991-2020 – Weather cities

Increased heatstroke

This is an important fact that shows the evolution of the French climate: the sun is high over the whole territory! Between 1981-2010 and 1991-2020, the average number of hours of sunshine during the year increased significantly in most of our regions. Paris went from an average of 1662 hours to an average of 1717 hours of sunshine. The increase is even more evident in Nantes, going from 1791 hours to 1873 hours of sunshine. It is however La Rochelle that holds the prize with an increase close to 200 hours ! The city has gone from an average of 2106 hours of sunshine per year to an average of 2303 hours per year!

Evolution of the number of rainy days (at least 1 mm) per year between the periods 1981-2010 and 1991-2020 – Weather cities

This general increase in the number of hours of sunshine is undoubtedly related to the increase in the frequency of high pressure periods in France, which appears to have accelerated in recent years.

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