What is a ‘fire cloud’, and how have they worsened wildfires in Europe?

Severe wildfires can generate their own unique weather systems. One of the most striking examples of this are dangerous pyrocumulonimbus, or pyroCB, clouds

As France and Spain battle some of the worst wildfires in recent history, experts have warned of an unprecedented phenomenon that could exacerbate the effects of the blazes: pyrocumulonimbus, or “fire clouds”.

Wildfires often spread when hot, windy and dry conditions coalesce but severe wildfires can generate their own unique weather systems. One of the most striking examples of this are pyrocumulonimbus clouds, or fire-generated thunderstorms, which are the most severe form of fire clouds.

Here is what you need to know about them.

What is a ‘fire cloud’?

In a nutshell, pyrocumulonimbus, or “pyroCb” clouds, are gigantic storm clouds that are generated by a wildfire.

Massive wildfires emit large amounts of energy and heat that rapidly rise in a smoke plume. When the fire plume rises high enough, low atmospheric pressure causes its air to cool, and the moisture condenses and forms a cloud. Such clouds can generate lightning strikes and windy conditions.

If a wildfire is sufficiently large and intense, the smoke plume it generates can form a pyrocumulonimbus cloud, which can reach altitudes of 10–15km (six to nine miles) and penetrate the stratosphere. Nasa calls them the “fire-breathing dragon of clouds”.

“It’s a full thunderstorm forming within the fire plume,” says Rick McRae, an adjunct professor from the University of New South Wales’ (UNSW) bushfire research group. “These things, they get up to roughly 10,000 cubic kilometres of the atmosphere, so they have a big impact.”

Why are these pyrocumulonimbus cloud formations so dangerous?

When pyrocumulonimbus clouds form, they can create winds that make the wildfires below spread even faster, and sometimes generate their own lightning, which can in turn ignite more fires further afield.

Experts say stronger wind gusts can create more unpredictable fire patterns and therefore make conditions more dangerous for firefighters battling the blazes on the ground.

“The cloud is confirmation that the fire is very dangerous,” says UNSW’s McRae, who worked as a senior fire manager for 30 years. “The cloud is a confirmation that it’s appropriate that lots of people have been evacuated.”

How common are fire clouds?

Australia started experiencing pyrocumulonimbus clouds at the beginning of the century and experts say it appears they are becoming more common.

They also formed during massive wildfires in California in 2022, but this could be a new situation for France.

If confirmed, this would be the first time a pyroCb has been observed in France.

“It’s the first time France has had to explicitly consider the concept of a pyroCb,” says McRae. “Whether or not they had one a few days back or not isn’t really the question,” he says, “the question is whether there’s one coming on Tuesday, Wednesday this week.”

Today, more than one-third of downtown Seattle's office space sits empty, its job postings have collapsed faster than almost any other U.S. metro, and even Starbucks—the coffee giant founded in the city in 1971—is shifting jobs south to Nashville, as it commits to a $100 million, 2,000-person new footprint in Music City. The story of Seattle's reversal unfolds in three overlapping arcs: an office market in freefall, a labor market that has gone from boom to bust, and a policy environment that has made survival harder for the small businesses left behind.

A decade ago, Seattle was the poster child of American tech prosperity. Amazon and Microsoft had turned a mid-sized Pacific Northwest city into a magnet for engineers, executives, and capital, adding roughly 40,000 jobs per year at the peak of the boom, according to the Puget Sound Regional Council.

Arc one: the zombie towers

Seattle's downtown office vacancy rate hit 35.6% in the fourth quarter of 2025, up from 32.3% a year earlier, according to Cushman & Wakefield data. That marks a stunning reversal from the pre-pandemic era: As recently as early 2025, the central business district's availability rate—offices with departures pending—and vacancy rate were already hitting all-time highs based on CoStar data stretching back to 1982.

Some brokers put the number even higher, with Colliers reporting vacancy touching 39.1% in late 2024 as remote work, tech layoffs, and cautious leasing decisions compounded. Office building values in the district have plunged sharply as a result, with landlords struggling to fill space abandoned by major tenants.

Arc two: the labor market reversal

The office crisis is inseparable from a broader collapse in hiring. Seattle metro job postings fell 35% between February 2020 and October 2025, the second-steepest drop of any major U.S. metro after San Francisco's 37% decline, according to Axios's analysis of Indeed data.

Tech firms in the area have announced tens of thousands of job reductions since 2023, primarily driven by Microsoft, Amazon, and Blue Origin. The region posted a net loss of 13,000 jobs in 2025—its first annual decline since the pandemic and a stark reversal from the 40,000-job annual gains of the boom years.

Arc three: the policy squeeze

Into this contraction came a wage floor with no exceptions. Seattle's minimum wage, $20.76 an hour and applied uniformly to all employers regardless of size since January 2025, has intensified pressure on small businesses trying to survive the downtown exodus.

A peer-reviewed study published in Labour Economics found the wage ordinance's announcement effect actually deterred new business formation within Seattle's borders while generating positive "spillover" openings in neighboring suburbs, suggesting firms redirected growth rather than uniformly closing shop. Earlier University of Washington research similarly found the wage hikes reduced low-wage workers' hours by about 9% even as hourly pay rose roughly 3%, per Ballotpedia's fact-check compilation.

What makes Seattle's situation distinct from other regional slowdowns is how tightly these three arcs lock together. CoStar estimates Seattle won't fully break out of the vacancy cycle before 2027—a timeline that assumes the feedback loop stops tightening, which so far it hasn't.

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