RENO, Nevada - Tripledigit heat across much of the western United States hampered crews battling scores of wildfires on Thursday, including one threatening dozens of structures in Montana and another that temporarily shut down the main route to the Burning Man counterculture festival in the Nevada desert.

 

Thousands of people have been driven from their homes amid hot weather in Oregon, Montana and California, where a blaze burned 10 homes and threatened 500 more near a hard-hit community and another closed a popular road to Yosemite National Park.

 

A wind-driven wildfire ripped through parched forest and grasslands in southeastern Montana, threatening 35 homes and structures and forcing the evacuation of an undetermined number of residents scattered in the area.

 

The fire that started on Wednesday in Custer National Forest, about 50 km west of Broadus burned at least 121 square kilometers in a single day.

 

Another fire about 96 km south of the Canadian border destroyed five cabins and five other structures and threatened 130 more buildings in the mountains south of Havre.

 

In Nevada, more than 70,000 people were expected at the Burning Man art and music celebration in the Black Rock Desert by the time it culminates on Saturday night with the burning of a towering effigy, and the vast majority got there by a state highway that was closed for several hours because of the fire.

 

"The traffic is moving, but you had a lot of congestion built up so it's very slow going," said Dan Gordon of the Nevada Highway Patrol.

 

The lightning-sparked fire has burned about 207 square kilometers and is about 64 km south of the festival.

 

Seven ranches were threatened, but there was no threat to the festival and there were no reports of injuries.

 

"It's not close to Burning Man at this time," Interagency Fire spokesman John Gaffney said. "There's a considerable distance between the fire and the festival. At this point, the goal is to keep the road open as much as we can."

 

Gaffney said the heat, expected to hit 37 C again on Friday, was one of the biggest concerns for crews fighting the flames by the air and ground. It's chewing through dense brush, and high temperatures were expected through the weekend.

 

Burning Man spokesman Jim Graham said the festival airstrip, which is built each year, is open and the celebration was continuing as scheduled.

 

"At the moment there is no impact," he said.

 

Other fires in Nevada closed a 90 km stretch of highway just south of the state line with California and burned a remote part of a vast former nuclear proving ground.

 

Nevada National Security Site spokesman Tracy Bower said the fire covered almost 10 square kilometers but wasn't considered a threat to people or buildings.

 

In Northern California, Governor Jerry Brown has declared a state of emergency and said the blaze there has destroyed multiple homes, but neither he nor the US Forest Service have said how many.