Smoke from widespread wildfires in Canada prompted air quality alerts across several Midwest and Northeast U.S. states this week.

The smoke is expected to remain over the northern and central Plains of the United States for the next couple of days, according to meteorologists.

Last week, Canadian wildfire smoke blanketed Wisconsin and caused the Air Quality Index to reach the unhealthy level for sensitive groups. Six days later, on July 31, the smoke appears to have a worse impact on the air.