Wildfires can get so hot they create a rare "fire thunderstorm" with intense dry lightning.

Wildfire season is here, and in some places, fuel is being added to the fire by the occurrence of a "fire thunderstorm. These fire-induced storms are rare but can be incredibly destructive, and happen when an exact set of conditions all happen at the same time. Scientists are working to better understand why they happen and interest has grown worldwide in the last few years as more of these storms occur.

When conditions are unstable enough, the extreme heat from the fire combined with enough moisture in the air creates the rare phenomenon of a “fire thunderstorm”, which occurs when pyrocumulus clouds form. These are clouds that form from very hot rising air on the surface, the intense heat of wildfires will force smoke and hot air to rise quickly. Once the air rises into the cooler troposphere (the lowest layer of the planet's atmosphere), the air cools and expands in the lower air pressure. The storms can produce intense clouds to ground lightning, and if there's enough moisture in the air, it will condense and form the giant dark clouds. 

James Haseltine, Oregon Air National Guard / Public domain.

The tops of these clouds have been described as the top of a head of cauliflower and are gray and brown—they can also reach as high as 30,000 feet! These clouds can produce rain, if there's enough moisture, and may turn into a pyrocumulonimbus. The rain can sometimes aid in fighting the fire, although that's a very rare occurrence. Powerful winds from the storms can be destructive and spread the blaze very quickly, making conditions suddenly far more intense. 

Scientists have learned that these storms act like volcanos, shooting ash, soot, and other aerosols into the stratosphere and have been researching the long-term weather and climatic effects of fire-induced thunderstorms. Scientists from the United States Naval Research Lab proved that these storms can have as much energy and impact as a moderately sized volcanic eruption. It has been discovered that the particles stay in the atmosphere for days, weeks, and sometimes months. In one case, Canadian researchers found smoke from a pyrocumulonimbus that occurred in 2017 in the air eight months after the storm.

Watch the video below that shows a pyrocumulus storm forming over a wildfire in Queensland, Australia, in 2016:

Because these storms are almost impossible to forecast, and wildfires are unpredictable, it's hard to prepare and prevent them. Wildfire conditions are constantly changing, and as more of these firestorms occur, they can be studied and perhaps give insight into how to better predict them.

In 2018, one occurred over the Carr Fire near Redding, California. That storm was so strong it created a fire vortex with surface wind speeds above 143 miles per hour. It was the first-ever fire tornado in the United States and the second-ever in recorded history. 

One of these fire-induced thunderstorms happened in Colorado earlier this week where several wildfires are burning. An update from the Pine Gulch Fire incident management team reported that winds gusted up to 40 miles per hour for three or four hours. Frequent cloud-to-ground dry lightning likely ignited more flames as it hit the dry terrain. 

While there is little that can be done to prevent a fire thunderstorm from occurring, a better understanding of them will help predict when one might happen, which can help prepare fire crews and save lives. As always in wildfire season, please be aware of conditions in your area and take all necessary precautions.