But then a dangerous shift in the weather occurred, turning a low-risk fire into a fast-moving threat within days, torching thousands of acres.

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.

Arizona Governor Katie Hobbs has demanded an independent investigation into why National Park Service staff let the fire burn during the driest time of the summer in a botched attempt to reduce wildf...