Shivering firefighters rejoiced as snow eased their battle against blazes that have blackened more than 1 million acres, but a forecast for warm, dry weather kept them on guard.

"I just love it. It means we might get to go home earlier," firefighter John Massey said Sunday as snow dusted much of Yellowstone National Park.Three to 4 inches fell in areas south of Mammoth Hot Springs. Humidity was as high as 90 percent, and temperatures in the mid-30s combined with winds of up to 30 mph for a wind chill index of 19 degrees.

"Things for the short term are better here," park spokeswoman Amy Vanderbilt said.

"We're more optimistic this morning than we have been for some weeks," said Bill Baden, Forest Service director at the Interagency Fire Center in Boise, in an interview Monday on CBS "This Morning." The center coordinates forest-fire fighting nationwide.

In the Sierra Nevada foothills of California, a wind-whipped fire that began Sunday charred 12,000 acres of brush and timber, destroyed 13 homes and seven to 17 other structures, and forced residents of Lake Wildwood, Calif., a town of 4,500, to evacuate Monday for a second time.

About 1,200 firefighters fought the blaze Monday in the historic Gold Rush country, said California Department of Forestry spokesman Charlie Jakobs. At one point, flames engulfed a bulldozer, forcing its operator to wrap himself in an asbestos blanket and take refuge under his vehicle. He suffered minor burns.

Light snow and low temperatures also helped firefighters in Idaho, and rain and cooler weather slowed fires in Colorado.

In northwest Oregon, officials closed millions of acres of state-protected forests in an effort to curb the number of fires caused by human carelessness.

In Montana, crews took advantage of the cool weather to carve lines around a forest fire north of Yellowstone and another that has scorched more than 30,000 acres in and around Glacier National Park near the Canadian border.

At Glacier, two firefighters were injured when a tree fell across the back of an open truck carrying crews to a 30,400-acre fire, officials said.

At Yellowstone, the light snow had firefighters shivering around propane heaters Sunday night. Fire managers joked that fears before the weekend of another "Black Saturday" _ when fires on Saturday, Aug. 20, sent blazes roaring across 150,000 acres _ melted when "White Sunday" arrived.

Firefighters were pulled off the lines Sunday when the chill set in.

"Our hoses were freezing up as fast as we put them out," said Wayne Jones, a fire crew chief from Bushnell, Fla.

Monday's forecast was almost as good as Sunday's weather: a chance of rain or snow, temperatures no higher than the 50s and light winds.

But by Tuesday, a drying trend is expected, with temperatures climbing back into the 60s and 70s.

"In five or six days we could be back in a more severe weather situation," Baden said.

Firefighters took advantage of Sunday's good weather to shore up their defenses against the wildfires, which have blackened about 900,000 of Yellowstone's 2.2 million acres since June in what firefighters call the worst fire season in the West in 30 years.

The weather allowed park officials to reopen the west entrance and the road from there to Old Faithful and Madison Junction north of the famed geyser. The rest of the park remained closed to visitors.

Residents of park headquarters at Mammoth were allowed to return home but were told to be ready for another evacuation if flames from a 263,400-acre fire threatens the area again.

A 328,100-acre fire in the park's northeast quadrant expanded significantly, combining with an 87,500-acre fire. But weather conditions helped firefighting crews, enabling them to attack the blaze directly.

Cabinet officials, who toured Yellowstone National Park over the weekend on President Reagan's orders, said the fires must be extinguished, and said the policy of letting naturally ignited wildfires in national parks and wilderness areas burn unless they threaten property or people hasn't worked.

"The most important thing is to concentrate our efforts on getting these fires under control and then out," Interior Secretary Donald Hodel said Sunday at the Boise Interagency Fire Center in Idaho. The center coordinates Western firefighting efforts.

"The old policy has to be reviewed and altered," Hodel said. "Nobody who has seen it operate this year could say it was a success."