Warnings from the Idaho Department of Health and Welfare urge residents in Lemhi and Custer counties to stay indoors as much as possible.
Air quality in those areas has reached the purple "very unhealthy" category because of wildfire smoke, prompting the Department of Environmental Quality to forecast poor conditions for the next few days.
Older adults, children and those with medical conditions are advised to stay indoors as much as possible. All residents are advised to avoid heavy work or exercise outdoors during poor air quality.
Meanwhile in the Treasure Valley, green or "good" air quality has returned to the Boise, Caldwell and Nampa areas.