Firefighters battling devastating fires in France have had to contend with a new threat: immense fire clouds that create their own wind and even lightning that can spark fresh blazes.
Known as "fire clouds" or pyrocumulonimbus clouds, these ominous-looking thunderstorms are created by extreme wildfires and can exacerbate already dangerous conditions.
This phenomenon, which is new to France, is yet another consequence of human-caused climate change, according to French researcher Jean-Baptiste Filippi, who studies wildfires.
As firefighters in southwest France struggle to bring a forest inferno under control before yet another heat wave descends on the country, Filippi told AFP about the phenomenon.
What is a fire cloud?
It is a storm where a column of air forms above a fire.
It starts off as a cute little white cloud—a cumulus cloud, which forms because water vapor has turned into tiny droplets.
As the sun heats the ground, the water vapor suddenly condenses. The cumulus becomes a much larger cloud, containing thousands of tonnes of suspended water.
Then, when the surrounding air becomes heated enough, it forms a column with an anvil-shaped cloud—the cumulonimbus.
This condenses even more air and generates more energy, with updrafts of more than 150 kilometers (90 miles) an hour.
It then rains, but the rain evaporates before it reaches the ground.
But it still cools the atmosphere where it falls, creating strong downdrafts.
Are fire clouds rare?
It is a common phenomenon in Portugal, California and Australia, where firefighters are more used to them. In Portugal, they had been rare until the deadly 2017 fires in Pedrogao Grande changed things.
In France, pyrocumulonimbus clouds are quite new. There were some in Landiras, south of Bordeaux, in 2022, but not for long.
Therefore, we need to learn how to manage fires that create their own wind—this is something relatively new.
Is climate change to blame?
Yes, it is. A consequence of global warming is more frequent heat waves. While thunderstorms are common in the region of this fire, thunderstorm conditions after three successive heat waves are a new combination.
Are they predictable?
Weather services can predict thunderstorms. But because these storms are located directly above a fire, we would need to know the fire's exact location in advance. That's impossible.
We can predict the conditions that will lead to these fires, but we won't know exactly where they are.
The biggest challenge is how unpredictable they are. The fire in France's southwestern Gironde region started with northerly winds, then westerly, then southerly, then easterly, then back again to the south, then the west...
On top of that, there is this potential energy in the atmosphere that meant that, locally, the convection column sucked up the embers and carried the fire further afield.
The local conditions became catastrophic, and the rate of the fire's spread was staggering.
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© 2026 AFP
Citation: What are 'fire clouds', the ominous phenomenon seen in France? (2026, July 27) retrieved 28 July 2026 from https://phys.org/news/2026-07-clouds-ominous-phenomenon-france.html
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