COEUR d'ALENE - Air quality is forecast to slowly begin deteriorating due to smoke from regional wildfires.

"It looks like it's going to be a gradual build-up to 'moderate' on the air quality index, a level down from 'good,'" said Shawn Sweetapple, air quality analyst for the Idaho Department of Environmental Quality in Coeur d'Alene.

A dry cold front moved through from Thursday night to Friday morning, which brought some wind and flushed out some pollutants, Sweetapple said Friday.

"It's been building back up," he said. "It won't be a quick blow-in like last month."

Winds are going to be light this weekend, and ventilation will be poor, so any smoke that flows in will likely stick around.

"This is if nothing changes," Sweetapple said.

Temperatures are to become quite hot Sunday and Monday, he said.

High pressure will be building into Monday.

In Washington state, fire officials are considering the use of explosives to build a fire break on an inaccessible section of a fast-growing wildfire near Ellensburg that has grown to nearly 14 square miles. The lightning-caused fire is being fought by more than 700 people.

A wildfire burning 10 miles north of Keller, Wash., on the Colville Indian Reservation, is threatening nearly 150 homes and other structures. Thirty-two residents living nearest to the fire have been evacuated and others have been told to be ready to leave at a moment's notice.

Elsewhere in the West, three firefighters have been injured battling a wildfire burning on the Idaho side of the Snake River across from Oregon and Washington.

Jill Cobb, a fire information officer, said one firefighter received a gash on his leg from a chain saw and required stitches. Another firefighter suffered heat-related problems and a third sustained a scratched cornea.

The fire on Friday grew to 76 square miles and destroyed a sixth structure.

The Associated Press contributed to this report.