Fire-breathing 'dragon clouds' appear over France and Spain, scientists warn of dangerous PyroCb phenomenon
As France and Spain battle some of their worst wildfires in recent history, experts warn of a rare and hazardous pyrocumulonimbus phenomenon appearing over the blazes for the first time, generating its own lightning and erratic winds that accelerate fire spread.
What are fire clouds?
Pyrocumulonimbus clouds, or pyroCb, are colossal thunderstorm clouds born from the heat of a massive wildfire. Unlike ordinary smoke plumes, these formations can punch through the troposphere into the stratosphere, reaching altitudes of 10 to 15 kilometres. NASA has described them as "fire-breathing dragons" because of their ability to generate lightning, hail, and violent downdrafts while feeding on the fire below.
It's a full-blown thunderstorm that forms within the smoke plume. These systems can occupy up to 10,000 cubic kilometres of atmosphere, so the impact is sweeping.
How a fire creates its own storm
A large wildfire releases enormous amounts of heat and moisture from vegetation. That superheated air, carrying smoke and ash, rises rapidly in a strong updraft. As the column ascends, atmospheric pressure drops, water vapour condenses, and a pyro-cumulus cloud appears. If the fire is intense enough, the atmosphere unstable, and upper-level moisture sufficient, the cloud continues to grow into a full pyrocumulonimbus, essentially a home-grown thunderstorm inside the smoke column.
Why they are so dangerous
Once a pyroCb forms, it can dramatically alter fire behaviour. The cloud produces local winds that fan flames in unpredictable directions, sometimes creating their own lightning strikes that ignite new fires kilometres away from the main front. Firefighters on the ground face sudden wind shifts and extreme turbulence, making suppression efforts far more hazardous.
The appearance of such a cloud is the ultimate confirmation that the fire has become extremely dangerous.
First appearance in southwestern France
French fire authorities in the Gironde department reported a "pyrometeorological phenomenon" over a major wildfire, calling it unprecedented for the country. The blaze, fuelled by high temperatures, drought, and strong winds, provided the perfect conditions for the cloud to develop. While pyroCb events are better known from Australia and North America, their emergence over Europe underscores how extreme fire weather is becoming more common in regions that previously rarely experienced it.
Similar conditions were observed in Spain, where multiple large wildfires are also burning, though the most dramatic cloud formation was documented over the French southwest. Experts caution that the smoke and soot injected into the stratosphere can linger for months and travel thousands of kilometres, potentially affecting air quality and climate patterns far beyond the fire zone.
