The Minnesota Pollution Control Agency (MPCA) has issued an “unhealthy for sensitive groups” air quality alert for southern, eastern and portions of central Minnesota from noon to 8 p.m. Friday. The affected area will include the Twin Cities, Marshall, Rochester, St. Cloud and the Tribal Nation of Upper Sioux.

The agency’s air quality index is expected to climb into the orange (unhealthy for sensitive groups) category Friday due to unseasonably warm weather, mostly sunny skies and high ozone levels moving in from the southern and central United States.

Smoke from wildfires in the western United States and Canada has dimmed skies over parts of Minnesota several days in the past couple of weeks. On Thursday, pollution levels were listed as yellow (moderate) over much of Minnesota because of “wildfire smoke particles, very warm temperatures and mostly sunny skies,” the MPCA said.

Higher ozone levels can aggravate conditions such as asthma, chronic obstructive pulmonary disease, chronic bronchitis and emphysema, and can affect children and teens and people doing heavy physical activity, such as playing sports or working outside.

If people experience severe symptoms, such as difficulty taking deep breaths, throat soreness, coughing or unusual fatigue, they are asked to contact their doctor.

Ozone is produced on hot, sunny days by a chemical reaction between volatile organic compounds and oxides of nitrogen.

For information on current air quality conditions and to sign up for daily air quality forecasts and alert notifications by e-mail, text message or the Minnesota Air mobile app, visit the MPCA’s website at

Conditions are expected to improve around sunset Friday as ozone levels decline.