A fire whirl, also known as a fire tornado or fire devil, is a rare phenomenon in which fire forms a tornado-like vortex of flames. Fire whirls can be formed in one of two ways: when a tornado spins too closely to a forest fire or when a heavy concentration of heat is generated in a small area. Typically, they're spawned from wildfires. Like tornadoes, fire whirls vary in size and duration; however, they typically last no more than a few minutes.
Although it's rare, this type of weather is extremely dangerous. In 1923, a fire whirl emerged during Japan's Great Kanto Earthquake and killed 38,000 people.