Hundreds of people remained out of their homes because of the threat of the Beaver Creek fire, Boise Public Radio reported.
One area that was ordered evacuated Friday was put on pre-evacuation status, allowing residents to return, possibly temporarily.
"We had winds gusting up to 30 mph, very dry air and the direction of the wind was blowing southwest to the northeast and a lot of the shape of the land in this area where fire is burning, a lot of valleys and ridges from the southwest to the northeast so they are lined up with the wind direction," Rudy Evenson, a fire information officer, said.
Areas under pre-evacuation status Saturday included the famous mountain resort of Sun Valley and the neighboring town of Ketchum, fire officials said in an incident report.
Evacuations were ordered Friday for 1,600 homes.
The (Spokane, Wash.) Spokesman-Review reported U.S. Forest Service Chief Tom Tidwell said the blaze has been designated the top priority wildfire in the country.
Tidwell, who toured the Beaver Creek fire lines with Idaho Gov. Butch Otter Friday morning, said there was "a chance" the fire could reach into the two resort communities.