Air quality in the Tri-Cities deteriorated Friday as a weather inversion trapped pollutants near the ground.
Benton Clean Air Agency data showed air quality at a level considered unhealthy for sensitive groups by early afternoon.
Those who should limit time outdoors include infants, children, pregnant women, senior citizens and people with health issues, including previous strokes, lung disease, heart disease, asthma or diabetes, according to Washington State Department of Ecology information.
Air quality issues could persist for a few more days.
The National Weather Service has issued an air stagnation advisory through 5 p.m. Monday for the Mid-Columbia. Areas of freezing fog also are possible through the weekend.
Officials are asking residents not to burn wood if they have another heating source in order to reduce the pollution.