225,000 people have been evacuated from the wildfires in south-western France, and we have not yet seen the end of them. Previous wildfires have shown that people tend to underestimate how rapidly they spread. Now, a frightening new phenomenon has emerged: a so-called pyrocumulonimbus, a gigantic smoke cloud that generates its own winds and lightning strikes, leading to additional fires.

“It is a David versus Goliath scenario. At some point, we have to find a weak point and attack there,” says Eric Brocardi, spokesman for the French firefighters’ union, the FNSPF.

He told France 24 that this is the first time the French fire service has had to combat such a phenomenon.

The phenomenon occurs when the fire causes air masses to rise rapidly in a column. The air mass then cools at higher altitude and forms a cloud – one that is unfortunately devoid of rainfall.

“This smoke cloud generates its own weather system and causes everything in its path to catch fire,” says Brocardi.

“Lightning strikes occur within the cloud and ignite embers on the ground, further fuelling the fire. It also produces a low, rumbling sound,” he says.

Such clouds have previously formed during wildfires in Australia and North America, but never before in France, according to Brocardi. They may also occur during volcanic eruptions.

The firefighters are at the mercy of the weather and the direction of the wind. Should the fire reach the city of Bordeaux, scenarios unprecedented in peacetime may unfold.