HAMILTON, Mont. (AP) _ Choking smoke veiled homes and businesses here Saturday as flames turned forest to ash just a few miles away in one of dozens of blazes that have made Montana a leading hot spot on the West's fire map.

``The Northern Rockies area is the hottest place in the country at the moment, and it's mostly Montana,'' said Lynn Pisano-Pedigo, spokeswoman at the National Interagency Fire Center in Boise, Idaho.

Montana's 16 largest fires had burned about 135,000 acres by Saturday, and smaller fires had blackened thousands more.

Across the West on Saturday, about 70 large fires were burning on more than 747,100 acres, according to the National Fire Information Center. The biggest, in Idaho, had charred at least 102,000 acres near the Montana border.

``Montana may not have the greatest amount of acreage, but it has more new (fire) starts and more severe weather, lightning going through,'' Pisano-Pedigo said.

``The weather system hasn't changed significantly in the last couple of weeks,'' she said. ``You do have the summer thunderstorms. But unfortunately, there isn't a lot of moisture connected with these. You get a lot of dry lightning.''

More than 300 homes have been evacuated in southwestern Montana's Bitterroot National Forest, and officials in the Hamilton area warned Saturday that more than 300 additional evacuations could be necessary. North of Missoula, residents of 12 homes fled Friday night, threatened by one of the state's smaller fires, a 2,000-acre blaze on the Flathead reservation.

A health alert in the Hamilton area advised those planning to remain to stay indoors because of the heavy smoke. In other parts of the state, dense smoke from fires south of Helena obscured the Capitol dome.

So far this year, more than 62,000 wildfires, mostly in the West, have burned 3.8 million acres. Assistant Interior Secretary Sylvia Baca has called it the worst fire season in 50 years.

Hundreds of Army soldiers and Marines have been sent to help weary civilian fire crews, and Forest Service chief Mike Dombeck announced Friday that 200 Canadian firefighters were coming to Montana to help.

Elsewhere in the West, a blaze 15 miles east of Jackson, Wyo., threatened several homes and cabins, but requests for more firefighters and planes to drop retardant were denied because of demand elsewhere, said Forest Service spokeswoman Mary Tyler. Some 200 people had been evacuated, many for four nights.

Wyoming got some rain from fast-moving thunderstorms Friday afternoon, but ``it was not enough rain to really be of any help to the firefighters,'' Tyler said. ``We would need several inches to help us.''

Idaho Gov. Dirk Kempthorne warned that the extensive fires burning in his state's rugged terrain probably won't be stopped until ample rain or snow arrives to finally extinguish them.

Mesa Verde National Park in Colorado was closed again by another rapidly spreading blaze on Friday, just hours after it had reopened after a 10-day, 23,000-acre fire. The latest fire in the nation's largest archaeological preserve doubled in size during the night, blackening 3,500 acres near some of the park's most popular sites by Saturday.

``There is no threat to the cliff dwellings,'' said Rob Morrison of the Durango, Colo., interagency dispatch center. ``They're down in a canyon and there is no way for the fire to get in there.''

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On the Net:

National Fire Information Center: http://www.nifc.gov

Forest Service links: http://www.fs.fed.us/fire/links2.shtml