By Laura Zuckerman
SALMON, Idaho, Aug 14 (Reuters) - A wildfire raging unchecked in the Idaho mountains has destroyed 71 structures, including at least a dozen homes, and was menacing two resort towns where nearly 1,000 summertime residents were evacuated this week, authorities said on Wednesday.
Much of the destruction wreaked by the blaze, burning in the steep, rugged forests of south central Idaho, was in a housing development near the town of Pine that is home to 53 of the structures lost, said fire information officer David Eaker.
The fire, whose menace is compounded by mountainous terrain, low humidity and thick smoke, is the latest to cause substantial property losses during a U.S. summer fire season that experts predict could become one of the worst on record.
Fire crews labored on Wednesday to protect houses in the threatened communities of Pine and Featherville by clearing brush and laying hose lines, and no homes have so far burned within the city limits.
But there was also no timeline yet for when residents of the towns might return home, and authorities said it would take hours, even days, to fully assess the extent of nearby damage from the so-called Elk Complex Fire, which started last Thursday.
Worsening conditions, including gusting winds, have prompted expanding evacuation orders in the last two days, including a renewed call on Tuesday for residents of Featherville to leave before it was too late, Eaker said.
"We are cautiously optimistic about what we can do to defend the towns but Mother Nature is in charge and she can deal some pretty rough cards," he said.
It was the second time in as many years that a massive wildfire has threatened Pine and Featherville, which were mostly emptied by Wednesday as the fire grew to nearly 112,000 acres.
The only road in and out of Pine and Featherville has been closed to all but fire personnel, and residents who leave the area are not being allowed to return. Fire managers were preparing for wind gusts of up to 30 miles per hour predicted for Thursday.
Meanwhile in Utah, a fast-moving blaze that broke out on Tuesday had destroyed at least 13 houses in affluent developments in the scrub oak and sagebrush foothills on the outskirts of Park City, fire officials said.
The so-called Rockport Fire in north central Utah is menacing an area where a single home can be worth as much as $50 million, said Park City Fire District Chief Paul Hewitt.
Authorities said evacuation orders would remain in place for the time being for the several upscale developments in the path of a fire estimated at 1,500 acres. The evacuation affects from 250 to 400 homes.
In western Colorado, a wind-stoked wildfire burning in mountainous terrain near Glenwood Springs threatens 20 structures and prompted the evacuations of several residents, the Garfield County Sheriff's Office said in a statement.
The so-called Red Canyon Fire has burned 350 acres and is 10 percent contained, but erratic gusty winds make its growth potential high. (Additional reporting by Keith Coffman in Denver; Editing by Phil Berlowitz)