More than 16 million residents in three Western states face heat warnings or advisories as wildfires scorched 100,000 acres and temperatures sizzled over 100 degrees.

That heat, plus high winds, helped Mother Nature get the upper hand in two large fires burning in Utah and Arizona.

Nine days ago in Brian's Head, a resort town in southern Utah, a man was burning weeds in his backyard. The winds picked up, and soon a hillside was on fire. That fire has now burned 67 square miles and forced the evacuation of 1,500 residents in 13 communities. So far, 21 buildings – 13 of them residential – were destroyed. Many owners are from Las Vegas who head to the mountains on weekends.

ARIZONA GOVERNOR SEEKING MORE WILDFIRE FUNDING

"You know there`s risk when you buy something in a forest, but you don`t anticipate it," said Pam Junge, who owns a home in Deer Creek. "You especially don`t anticipate it twice. We lost our home in Las Vegas in 2009 to a fire and had to rebuild. Lightning shouldn`t strike twice."

In Los Angeles, a motorist crashed into a tree Sunday, sparking a fire that quickly spread to 750 acres in about three hours. Police closed Highway 14 in both directions while firefighters attacked the flames from the ground and air.

But the National Interagency Fire Coordination Center says moisture in the southeast and snowpack in Rockies and Sierra mountains should keep fire activity below normal for July. But those massive winter rains in California means forests and the high desert are loaded with brush and weeds. That goes up like paper, meaning a single spark can turn into a big fire fast.

FIREFIGHTERS BATTLE INTENSE WILDFIRES IN UTAH, CALIFORNIA

The Frye Fire burns the western edge of the Pinaleño Mountains in Coronado National Forest above Ft. Grant Prison near Willcox, Ariz. on Thursday, June 22, 2017. (Kelly Presnell /Arizona Daily Star via AP)

The U.S. Forest Service says a drone Sunday grounded helicopters fighting a fire in northern Arizona near Prescott. It also happened Friday at a fire in New Mexico and four times in May at various fires, prompting the U.S. Forest Service to put out a public service announcement warning people not to fly drones near fires.