The Minnesota Pollution Control Agency (MPCA) has issued an air quality alert through 8 p.m. Friday, and it includes the seven-county Twin Cities metro area, St. Cloud and most of southeast Minnesota, including Rochester.
Per the alert, the air quality is expected to worsen Friday afternoon and become unhealthy for sensitive groups, such as people with lung disease (including asthma), heart disease, children and older adults, in addition to people who are active outdoors.
"Light winds over the past two days have caused the pollutants nitrogen dioxide (NOx) and volatile organic compounds (VOCs) to accumulate over the region. Sunny skies and hot temperatures will cause these pollutants to react in the air and form ozone," the MPCA explained.
Air quality is expected to improve after the sun sets.
Meanwhile, the Twin Cities metro area is under a heat advisory until 8 p.m. Friday. Temperatures are expected to rise into the upper 80s and low 90s, with heat index values – what it actually feels like outside – pushing 95 degrees.