Two wildfires in the western United States, including a megafire on the North Rim of the Grand Canyon, are generating 'fire clouds' that create their own erratic weather systems. The wind-whipped fire in Arizona has destroyed the Grand Canyon Lodge and charred over 164 square miles, making it the largest fire currently burning in the continental US and one of the top ten largest in Arizona history. It is only 9% contained.
In Utah, a separate fire near Monroe has burned 75 square miles since 13 July and is 11% contained. Evacuation orders were issued for several towns, and scorched power poles led to electricity shut-offs in nearby communities. Utah Governor Spencer Cox declared an emergency on Thursday and planned to visit the affected area.
Pyrocumulus clouds have been observed over the Arizona blaze for seven consecutive days. These towering convection clouds form when air above the fire becomes superheated and rises, creating giant billowing columns visible for hundreds of miles. Fire information officer Lisa Jennings warned that they can fuel the fire with dry, powerful winds and create downdrafts that pose dangers to firefighters.
In Utah, a more severe pyrocumulonimbus cloud—dubbed a 'fire-breathing dragon of clouds' by NASA—caused rapid winds when a smoke column collapsed. This type of cloud recently generated a fire tornado in eastern Utah with wind speeds estimated at 122 mph. Multiple fire crews in Utah were forced to retreat on Wednesday due to the unpredictable conditions.
Atmospheric scientist Derek Mallia from the University of Utah explained that these clouds may become more frequent due to the climate crisis, which lengthens fire seasons and exacerbates drought. The Dragon Bravo fire on the Grand Canyon's North Rim, sparked by lightning on 4 July, surpassed the megafire threshold of 156 square miles. It has forced the closure of the North Rim for the season after destroying dozens of buildings.
Fire behaviour analyst Arthur Gonzales noted that pyrocumulus clouds over the Arizona fire have reached heights of at least 25,000 feet and could go higher. Despite strong winds, their consistent direction has aided fire management efforts. However, historically dry conditions with single-digit humidity and low fuel moisture continue to challenge containment.
