It is the first time that this weather phenomenon, the pyrocumulonimbus cloud or fire cloud, has been observed in France.Image: Keystone
Also feared by firefighters: A firestorm caused by forest fires is raging in France, producing a scorching hot cloud with its own weather.
Jul 28, 2026, 3:54 amJul 28, 2026, 3:54 am
Anna-Lena Janzen / t-online
The devastating forest fires in southwest France have seen a phenomenon that even hardened firefighters fear: a firestorm created by the fires that produces a blazing hot cloud with its own weather.
In most cases, the firestorm cannot be extinguished or brought under control, explained Brocardi. The winds constantly change direction. “The result is that it spreads in all directions and forms several fire fronts, which makes the situation completely unpredictable.”
“This is unprecedented,” said Eric Brocardi, spokesman for the French fire service association FNSPF. “It’s a David versus Goliath scenario,” Brocardi told AFP. According to him, the firefighters are hoping for a “weak spot” that they can address.
300,000 people evacuated
By the weekend, more than 300,000 people had been forced to flee because of the fires in France and Spain. In France, the flames raged primarily in the southwest of the country, where, according to Interior Minister Laurent Nuñez, they recently spread “uncontrollably” near the city of Bordeaux. On Sunday they moved within 15 kilometers of the city limits.
According to the prefecture, 42,000 hectares of land in the Gironde have so far fallen victim to the flames. According to official information, 250,000 people in France were affected by an evacuation order by Sunday afternoon. At least 240 houses were destroyed in the Bordeaux area alone, many of them in the municipality of Le Porge. At the weekend, around 2,500 firefighters, 1,500 military personnel and around 1,200 police officers took part in the operations against the flames in the Gironde department.
Lightning and hurricanes from the fire cloud
The cloud, also known as Cumulonimbus flammagenitus, forms when air near the ground heats up so much that it quickly rises together with smoke, water vapor and ash, often several kilometers high into the stratosphere. There the mixture meets cooler air masses and creates its own weather system with strong winds that further fuel the fire.
Violent thunderstorms occur, which usually lead to little rain but to violent lightning. These can also ignite new fires at great distances – in some cases over 30 kilometers away. Lightning often shoots from the cloud to the ground and a rumbling noise is created. In addition, strong gusts occur near thunderstorms, sometimes with hurricane force. They quickly cause new large areas to burn, especially when the vegetation has dried out.
“A war-like scenario”
In most cases, the firestorm cannot be extinguished or brought under control, explained Brocardi. The winds constantly change direction. “The result is that it spreads in all directions and forms several fire fronts, which makes the situation completely unpredictable.”
According to Brocardi, there are only two ways out: Either it rains, “and it would have to rain heavily for three days.” Or “we find a way to direct the fire to a place where it goes out by itself – for example by the sea.”
With the cloud of fire in southwest France, firefighters could only retreat. «We must recognize that this force of nature is beyond our control. It’s a war-like scenario where we are constantly under fire and we all have to get to safety.”
Then only “stoicism” helps, explains Brocardi. In addition to directly fighting fires, the fire department can do a lot – such as defending strategically important points and bringing animals to safety from the flames.
This phenomenon is becoming more common worldwide
The phenomenon had been known to scientists for a long time, but because it occurred so rarely, it was not researched in more detail. However, the number of pyrocumulonimbus clouds occurring has been increasing significantly in recent years. They have been spotted more frequently in Bolivia, California, Russia and especially Australia in recent years.
NASA writes about the phenomenon it calls the “fire-breathing dragon”: “These fire-generated clouds are associated with extreme fire behavior that hinders firefighting efforts and can devastate communities.” The space agency highlights the need to better understand clouds “given the ongoing and projected increase in fire activity and severity.”
Overall, the risk of large, devastating fires is increasing worldwide due to the climate crisis. Humans often cause fires, and due to global warming and drought, our forests and savannahs are becoming drier and more susceptible to fire.