U.S. land managers are racing the clock as hotter, drier weather raises the risk of wildfires in the nation’s overgrown forests with each passing year. One tool is to use the flames from lightning-sparked wildfires when conditions allow or to plan prescribed fires for other times of the year to clear out dense vegetation

What fueled the explosive growth of the Dragon Bravo Fire was a mix of gusty winds, dry air and above-normal heat – weather conditions experts described as atypical for this time of year, when monsoonal moisture typically tamps down wildfire risk across Arizona.

A water treatment facility at the North Rim had been compromised by the fire, causing chlorine gas to fall towards the bottom of the canyon.