• The summer of 2021, which follows four unusually hot summers, gave the impression of being cold and rainy in the Hauts-de-France.

  • Since 1960, we have noticed that two out of three summers have been colder than that of this year.

  • Overall, there is a third of excess rain over the summer as a whole compared to the usual average, with a record in Maubeuge and Thiérache.

Summer 2021 ends on Tuesday.

And in Hauts-de-France, one has the impression that it never started.

However, weather statistics show that the effect of freshness felt must be qualified and is not historical.

“This summer simply follows four unusually hot and sunny summers,” explains Jean-Michel Meunier, from the climatology department of Météo France.

Hard return to the reality of the northern climate.

A cold summer?

Not really

Overall, the region has experienced the coldest summer since 2014. But if we take a step back since 1960, we see that two out of three summers have been colder than this year.

It was therefore rather hot.

This rotten summer impression also goes through the maximum temperature recorded in Lille.

It did not exceed 30.4 °, far from 41.5 ° in 2019 and 38.9 ° in 2020. You have to go back to 1993 to have such a low maximum temperature.

“The global warming effect is clearly visible, notes Météo France.

Because until the end of the 1960s, we almost never reached 30 °.

"

In detail, month by month, it was above all August which slipped (-1.2 °) compared to the average established between 1980 and 2010. On the other hand, the month of June was warmer (+2.6 %).

The hottest areas are Maubeuge and Steenvoorde, in the North and the L'Authie valley, in Pas-de-Calais.

Those where it was coldest are the Deux Caps and the area between Compiègne, in the Oise and Château-Thierry, in the Aisne.

Very little sunshine

Compared to the last four years, unsurprisingly, the sun deficit is clearly visible.

We observe, on average, one hour of sunshine less per day, both in Nord-Pas-de-Calais and in Picardy.

The sunniest areas are on the coast.

With 546 hours of sun over three months, the North also recorded its lowest level since 2014. If we only take into account the month of August, we have to go back to 2011 to have so few hours of sun .

The record for the grayest summer remains 2007 with 450 hours.

The sunniest remains the summer of 1976, known as the “drought” with 846 hours.

As water, water everywhere !

Overall, there is a third of excess rain (264 mm) over the summer as a whole.

"It is indicative of a very wet summer," confirms Météo France.

For twenty years, only five summers have been more watered with a record in 2005 (331 mm).

But the situations were very disparate.

Thus, Maubeuge flirts with its historical record (379 mm, which represents 70% of precipitation compared to the average).

The Thiérache was also very affected (between 350 and 380 mm).

Conversely, in Calais (185 mm) or Valenciennes and Cambrai (191 mm), between Amiens and Beauvais (below 200 mm), the summer was rather dry.

The risks of drought?

"The rainy summer allowed the tensions on the groundwater to be less strong, especially for withdrawals for irrigation, notes the Regional Directorate of the Environment (Dreal).

However, part of these rains were more violent and concentrated, causing a lot of runoff on the soils, which does not provide any useful character for the vegetation.

"

Another phenomenon observed: the wind has greatly dried up the vegetation.

“There has been no groundwater recharge because what is taken and what feeds the water is always negative,” says Dreal.

These aquifers are in a normal state but offer no guarantee that new episodes of drought will not appear, especially if the winter rainfall is low and irregular.

"

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