LAME DEER, Mont. • Wildfires tearing through eastern Montana and elsewhere in the U.S. West are devouring vast areas of rangeland that cattle ranchers depend upon, setting the stage for a potential shortage of livestock forage as the hot, dry summer grinds on.

On the Northern Cheyenne Indian Reservation, firefighters and local authorities scrambled to save hundreds of homes in the path of a fire that started Sunday and exploded across more than 260 square miles in just a few days, triggering evacuation orders covering thousands of people. Some ranchers stayed behind to help. Yet as flames charred mile after mile of rangeland and forest, fire crews could do little to protect cattle pastures that are crucial to economic survival for some families on the remote reservation.

As the fire raced across the hilly reservation, tribal member Darlene Small helped her grandson move about 100 head of cattle to a new pasture, only to have to relocate them twice more as the flames from the Richard Spring fire bore down, she said Thursday. An extreme drought that’s blanketing the West has made matters worse for ranchers by stunting vegetation untouched by fire.

“They’ve got to have pasture where there’s water. If there’s no water, there’s no good pasture,” Small said. Particularly hard hit were some ranchers already depending on surplus grass after a fire burned them off their normal pasture last year, she said.

Meanwhile, California’s Dixie fire — which started July 13 and is the largest wildfire burning in the nation — threatened a dozen small communities in the northern Sierra Nevada even though its southern end was mostly corralled by fire lines.

The fire has burned 790 square miles, destroyed some 550 homes and nearly obliterated the town of Greenville last week. It was 30% contained. The Montana blaze began Sunday and winds gusting up to 56 mph caused it to explode across more than 260 square miles by Thursday. Primed by heavy, swirling winds and hot temperatures, it was spreading in multiple directions, torching trees and sending off embers that propelled the flames across the dry landscape.

It’s crept within about a mile of the eastern edge of the evacuated town of Lame Deer, Northern Cheyenne Tribe spokesperson Angel Becker said. The fire passed over a highway where officials had hoped to stop it, putting the southern portion of the reservation at increased risk, officials said.

Lame Deer, a town of about 2,000 people, is home to the tribal headquarters and several subdivisions and surrounded by steep, rugged, forest.

As it closed in on the east side of town and a second fire ignited to the west, tribal officials late Wednesday urged residents who did not heed the initial evacuation order to flee. Buses moved people to a school in Busby, about 15 miles away, and to the shelter set up on the nearby Crow Indian Reservation.

“We had some people who refused, but the majority of our elders and women and children had definitely left with that last push,” Becker said.

Firefighters worked into early Thursday around Lame Deer to keep the blaze from destroying houses. No houses were reported destroyed but fire officials continued assessing the damage. More than dozen sheds and other outbuildings were lost, they said. As flames rose from both sides of a narrow valley and smoke choked the air, rancher Jimmy Peppers sat on his horse east of town, watching a glow intensify over the site of his house.

A tree goes up in flames Wednesday as a wildfire burns on the Northern Cheyenne Indian Reservation near Lame Deer, Mont.