More than 1,000 firefighters have raced to the scene to contain the blaze, Xinhua reported Sunday.
The Elk Complex fire, burning for the past nine days, has destroyed 81 structures and over 125,000 acres of land, fire officials said.
Around 80 km to the west, the Beaver Creek fire was spreading rapidly and threatening the historic "wild west" town of Hailey, the seat of Blaine county with around 7,900 residents.
The fire has forced the evacuation of 2,250 homes and 7,000 people, Blaine County Sheriff Gene Ramsey wrote on Twitter.
"It's heading straight for Hailey. The flames are towering above the town and are clearly visible to the residents," said Bronwyn Nickel, public information officer for Blaine County. "We're telling residents to get out."
The fire, spreading in all directions due to winds, is still considered a major threat to the wealthy ski town of Sun Valley and the larger old town of Ketchum, where American writer Ernest Hemmingway lived and died.
"It is spreading right up the river valley ... through heavy vegetation and wooded areas," said Nickel.
He said extremely dry and hot conditions have accelerated the fire.
In addition to the firefighters, an extensive array of local and national aircraft have been deployed, the National Interagency Fire Center (NIFC) said.
With no loss of life and only minor destruction reported so far, both fires seem mild compared to those in June in Colorado that burned more than 500 homes, and in Arizona that killed 19 firefighters.
Both Idaho blazes started by lightning, the NIFC said.
Nearby, the Pony Complex fire that began Aug 8 is now 90 percent controlled, after destroying over 149,000 acres, the NIFC reported.
With all the blazes so far affecting more than 400,000 acres, Idaho appears to head towards a record year of destruction from wild fires.
--IANS (Posted on 18-08-2013)