The Minnesota Pollution Control Agency issued an air pollution health alert and advisory for sensitive groups in western and southern Minnesota until Friday.
The MPCA says a strong temperature inversion, snow melt and fog are trapping fine-particle pollution near the surface, causing unhealthy levels for sensitive groups, according to the Associated Press. The alert affects western Minnesota and is in effect until Friday at noon.
An air pollution health advisory is in effect for the southern half of Minnesota, including the Twin Cities and Rochester, from Thursday evening into Friday morning.
Fine-particle concentrations across the southern half of the state are expected to be moderate throughout the day, but as wind speeds decrease and temperature inversions form and strengthen overnight, fine-particle concentrations are expected to increase and may reach unhealthy levels for sensitive groups, the MPCA says.
Sensitive groups include the elderly, children, people with cardiovascular or respiratory diseases, and people engaged in strenuous activity indoors or outdoors, the Associated Press reports.
These conditions are expected to improve when a cold front moves across Minnesota Friday, bringing cleaner air into the region, the MPCA says.