Wildfires can spin up more than smoke and flame. Under the right conditions, the rising heat above a fire begins to rotate, pulling burning debris and superheated gas into a twisting vertical column that behaves like a small, fire-fed tornado. These fire whirls have always been part of extreme fire behavior, but fire scientists and incident commanders are documenting them more often as wildfires themselves grow larger, hotter, and more erratic across the western United States and other fire-prone regions.
What Meteorologists Mean by a Fire Whirl
The National Wildfire Coordinating Group defines a fire whirl as a spinning vortex of ascending hot air and gases rising from a fire, carrying flame, smoke, and debris upward inside its rotation. The phenomenon ranges enormously in scale, from vortices barely a foot across that flicker for a few seconds to columns hundreds of feet wide that persist for several minutes. Firefighters sometimes call the smallest examples “fire devils,” a nod to the harmless dust devils that form on hot, calm days, but the largest fire whirls behave nothing like their tame cousins.
How a Wildfire Builds Its Own Vortex
A fire whirl forms the same way any rotating column of air forms: something has to start the spin, and something has to stretch it vertically. A wildfire supplies both ingredients on its own. Intense heat above the flame front creates a powerful updraft as hot air rises and pulls cooler air in behind it. When that updraft runs into a crosswind, uneven terrain such as a canyon or ridgeline, or turbulence from the fire burning unevenly across a hillside, the rising air begins to rotate. As the spin tightens and stretches upward, it can pull flame and embers directly into the vortex, in much the same way a figure skater speeds up by pulling in their arms.
From Dust-Devil Size to City-Block Size
Most fire whirls stay small and burn out within a minute or two, but the largest documented examples have carried the destructive force of a small tornado, according to the National Environmental Satellite, Data, and Information Service, which studies the most extreme fire-driven weather. A large fire whirl can snap trees, toss debris, and lift burning material high enough that embers drop well beyond the main fire’s edge, igniting new spot fires ahead of crews who are still working the original perimeter. That combination of wind, heat, and flying embers is part of what makes large fire whirls one of the more feared forms of extreme fire behavior rather than simply a dramatic photograph.
How Investigators Rate the Largest Ones After the Fact
Because a fire whirl is too dangerous and unpredictable to measure directly with instruments while it is active, investigators typically reconstruct its strength afterward the same way storm surveyors handle a tornado: by examining which trees were snapped versus uprooted, how debris was scattered, and how nearby structures were damaged. Using that method, some of the largest fire whirls documented in wildfires have been assessed as comparable in wind speed to a weak-to-moderate tornado, strong enough to move vehicles and topple weakened trees even though the vortex itself may last only a few minutes. That kind of after-the-fact survey work is also how researchers have been able to compare fire whirls across different wildfires and confirm that the largest, most damaging examples tend to form during the same extreme-fire-behavior conditions that produce bigger fire-generated storm clouds.
Why Bigger Wildfires Are Producing More Fire Whirls
Fire whirls are closely related to an even larger phenomenon: the pyrocumulonimbus, or fire-generated thunderstorm, that can form above the most intense wildfires. NASA’s research on wildfires and climate change has tracked a rise in these fire-driven storms as wildfires themselves have grown larger and burned hotter; researchers have noted that Australia’s 2019-2020 bushfire season alone produced roughly as many fire-generated storms as had been recorded across the previous two decades combined. Fire whirls form under many of the same conditions that produce those bigger fire clouds, so as wildfire seasons trend toward larger, higher-intensity burns, the conditions favorable to fire whirls are simply occurring more often.
The Added Danger of an Unpredictable Vortex
Unlike a storm-spawned tornado, which tends to track in a relatively continuous path that spotters can follow, a fire whirl can change direction with little warning, following shifts in the fire’s own convection rather than a broader wind pattern. That unpredictability is precisely why fire behavior analysts flag terrain and wind combinations known to favor whirl formation before crews are sent in, and why a fire whirl spotted from a distance is treated as a serious hazard rather than a curiosity. As documented in the broader research on fire whirl formation, the vortex’s combination of speed, heat, and erratic movement is what separates it from an ordinary gust front, and it is a major reason incident commanders now train crews specifically to recognize the conditions that produce one before it forms.
This article was produced with the assistance of AI and reviewed by Morning Overview editors.
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