High levels of ozone pollution (smog) are being forecast by the Puget Sound Clean Air Agency for the Cascade foothills of King and Pierce counties and are expected to reach the “Unhealthy for Sensitive Groups (USG)” category. These conditions will develop over the course of this weekend as the region comes under the influence of a hot and stagnant weather pattern.

Exposure to ground-level ozone can trigger asthma attacks, make breathing difficult, exacerbate lung and heart problems and weaken the immune system. The Washington State Department of Health recommends that people who are sensitive to air pollution limit time spent outdoors.

Air pollution is especially harmful to children, people with heart and lung problems, and adults over age 65.

Smoggy conditions will mostly impact communities in the Cascade foothills of King and Pierce counties.

Air quality is predicted to decline beginning on Saturday afternoon into the Moderate category. Conditions are expected to worsen to USG levels by late Sunday and remain through Wednesday night.