“It’s nonsense”: thunderstorms, heat spikes and sudden temperature drops… why is the weather so unstable ?

For three weeks, the sun has been coming and going in France. The region is not immune to this instability. After an episode of storms and showers, the good weather returned this week but is not expected to last. We will explain to you what these disturbances are due to.

"It’s been nonsense this time." On the Place de la Comédie, Montpellier residents have been enjoying the sun since this weekend, very happy to finally see a lull.

Between stormy showers and sudden heat, they no longer know what to wear, when to water their gardens or book their vacation. "We don't know how to dress anymore. In the morning when I leave I'm cold, at midday it rains, in the evening I come home from work and I'm cold, castigates a passerby.  Difficult to navigate, when will summer return??

You will have to be patient

President of Predict Service, a Montpellier-based company specializing in the prevention of weather risks, Alix Roumagnac explains to Midi Libre that the situation should last until the end of May. When we want to talk about the weather, two phenomena oppose each other: on the one hand the depression, responsible for bad weather, and on the other the anticyclone, which allows on the contrary to clear the cloud masses.

However, at the moment, "the anticyclone is not setting up, we are under the influence of a depression which comes from the’Atlantic", and which should remain for another one to two weeks. From the beginning of June, the sunny days will begin to set in. Against the "cold" spring, a very dry and very hot August is to be feared.

What will the weather be like in the region in the coming days ?

#Montpellier. After a sunny Thursday, thunderstorms are likely to break out on Friday afternoon. This weekend, the weather will be nice, peaks of 25 °C are expected on the coast.

#Nîmes. The sky will be quite cloudy until Friday when, as in Hérault, storms could occur in the afternoon and throughout the night. This weekend, the mercury will reach 29 °C.

#Alès. Although the thermometer rises to 23 °C on Thursday, this will not spare the city from a few storms from Thursday. Sunday, despite clouds, 29 °C are expected.

#Mende. It will rain Thursday morning, before thunderstorms arrive and last until Friday evening. The weekend will be cloudy, and temperatures will not exceed 22 °C on Sunday.

#Millau. The weather will be cloudy until Friday and a few drops of rain could fall. Heading into the weekend, a few storms are expected. It will be up to 24°C on Sunday.

#Carcassonne. Once is not customary, thunder is likely to rumble on Friday. But the sky will clear quickly and will bring mild weather, with temperatures going up to 27 °C.

#Narbonne. After fairly clear weather on Thursday, the city will in turn welcome a few storms at the end of the day on Friday. This weekend, the thermometer will read 27 °C.

#Perpignan. After the good weather, thunderstorms will darken the sky on Friday and until Saturday morning. This weekend, the sky will be cloudy intermittently, peaks at 22 °C are expected.

The fault is a "cold drop"

Between an anticyclone to the north of the continent, and another located further to the southeast, a "cold drop" is caught in a vice, just above France. "It’is a particular depression, which we call cold drop when there is very cold air at altitude", explains Alix Roumagnac. It led to the disturbances observed in recent weeks, stuck in an "anticyclonic blockage".

Which explains the violent rainy episodes, known as "Mediterranean" :"The cold drop went down to the Mediterranean, this led to the Mediterranean episodes that we saw in the spring in the region and throughout the south of France. The sea being very warm, evaporation causes bad weather. The sea, too hot, meets the cold drop, an altercation which often ends in precipitation.

And of course, climate change is partly responsible since it warms the seas and causes bad weather. But the climatic variability, it being natural, explains that from one year to the next, the weather – spring weather too – can change significantly, the specialist qualifies.

Is it really raining more this year?

Between March and May 2024, the rainfall excess in Hérault was between 40 and 70 %, note Info Climat. In Gard, it reached 155 % last week, and even 161% at the end of March. On the other hand, on the Lozère side, it is only 20%, and even in deficit in Aveyron with – 2%.

To the west of the region, the situation is more critical than average. Rain is no longer in excess, but deficit. Starting with the Pyrénées-Orientales, with a -35% deficit at the end of April. Despite the recent rainy-stormy episodes experienced by the department, the deficit only rose to -8%.