Weather. Severe thunderstorms in Burgundy-Franche-Comté: "The higher the temperatures, the greater the risks."

Are there more severe thunderstorms than before?

"A bit of both, I'd say. The climate is warming. The temperature is rising on average, year after year. So there's more and more water vapor in the atmosphere. In fact, there's potentially more rain, with sustained precipitation potentially occurring, particularly in the form of thunderstorms. The higher the temperatures, the greater the risk, because the difference with the cooler air at higher altitudes creates increasingly strong turbulence. This phenomenon can give rise to supercells. There have always been some, but they are becoming more and more frequent and more and more violent."

Do you know if there will be more thunderstorms this summer?

"It's likely. No one will be able to give you a forecast for the entire summer, at least not in a calm manner. We're heading straight down that path, because we've already been experiencing early episodes of very high heat for a week or two, and it's going to continue. This summer, these heat waves will return, unlike last year when the weather was less hot. We're back on a very hot cycle, with air rising from the Maghreb, Spain, etc."

Is there a time of year when thunderstorms are more likely?

"The mid-spring period, in May, is quite favorable. There are still unstable, humid residues, cool air, with warm air already rising. It is therefore a very favorable month for thunderstorms. In June, July, and August, there are also risks, everything depends on the weather configurations. Overall, in very hot summers, even if they are very dry, it doesn't take much in our regions to create humidity, and therefore instability. In September, there can still be thunderstorms, but less frequently."

How long does a thunderstorm last?

"The most typical ones last from 30 minutes to an hour. But we can have "geostationary" storms, which can last for more than an hour, sometimes two hours. They can cause very heavy rainfall. These are the famous supercells. But they are rarer."