The Dragon Bravo Fire in the North Rim of the Grand Canyon "exhibited extreme and volatile fire behavior" overnight and expanded to about 5,000 acres, fire managers said Sunday.

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...