The Minnesota Pollution Control Agency has extended an air pollution alert for the southern half of the state, including the Twin Cities, Rochester and Marshall through late Saturday.
The MPCA issues an air pollution alert when the amount of fine pollution particles in the air reaches a level that's considered unhealthy for certain sensitive groups.
Those groups include people with cardiovascular problems, young children and the elderly. The agency says people should be cautious about heavy exercise during the alert.
The alert began Thursday and was scheduled to end on Friday. But lingering light winds and high pressure continue to trap pollution in the air, leading the agency to extend the alert.
The agency says the amount of pollution particles in the air will peak on Saturday morning before returning to lower levels by Sunday.
A less serious air pollution advisory for central Minnesota, which includes Brainerd, Detroit Lakes, Duluth and St. Cloud, expired Friday.
Hourly air quality updates are available on the MPCA Web site.