The Minnesota Pollution Control Agency has issued an air pollution health alert for the Twin Cities and Rochester through 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.
Officials say light southeasterly winds and high pressure have caused the spike in pollution particles. Agency officials say they expect levels to increase through Saturday morning until a north wind disperses the pollutants by Sunday.