(Adds details, interview on Inyo fires)

By Jim Christie

SAN FRANCISCO, July 8 (Reuters) - Wildfires raged across the western United States on Sunday as firefighters scrambled to prevent flames from spreading across rugged terrain thick with tinder turned bone-dry by scorching weather.

Some of the intense blazes forced hasty evacuations of rural homes and recreational areas and officials temporarily shut highways and railways in some fire zones.

California, Arizona, Nevada, Utah, New Mexico, Oregon, Washington, Idaho and Montana each reported wildfires of varying severity as a heat wave blanketed the western United States.

Fanned by high winds, a fire in Utah grew into a massive blaze covering more than 160,000 acres (65,000 hectares). In neighboring Nevada a fire burning 30 miles (48 km) southwest of the town of Winnemucca consumed an estimated 152,000 acres (62,000 ha). The two fires forced temporary closures of major interstate highways.

Neighborhoods in Winnemucca were briefly evacuated with the approach of a separate fire that had burned an estimated 25,000 acres (10,000 ha) of brush.

"People are back in their homes now but we're keeping a very close eye on this fire," Jamie Thompson, a spokesman for the U.S. Bureau of Land Management, told Reuters. "There is a potential for extreme fire conditions today as well."

Lightning triggered both blazes near Winnemucca and fire crews are on alert for more strikes.

"Isolated cells were moving through the area. They had very little moisture but plenty of lightning," Thompson said. "There is still the potential for isolated thunder storms with lightning of course this afternoon."

In California, fires started by lightning in the Inyo National Forest forced evacuations of campgrounds. The two blazes have scorched an estimated 34,000 acres (14,000 ha) since Friday, according to the U.S. Forest Service.

The Forest Service imposed fire restrictions a week earlier in all Inyo National Forest lands and neighboring Bureau of Land Management lands, expecting increased fire danger from hot, dry weather.

"Everything is very, very dry," said Nancy Upham, a spokeswoman for the Inyo National Forest. "There are seasoned fire fighters who are seeing fire behavior they have never seen before ... Things are just igniting with a single spark."

More than 500 fire fighters are combating the Inyo fires, hoping for calm and predictable winds after strong and erratic gusts on Saturday, Upham added.

"The winds are the wild card," she said.

Fire officials across the western United States have been bracing for a busy fire season after scant rainfall this past winter.

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