Smoke from Canadian wildfires hovered over several Midwestern states Saturday, bringing warnings of unhealthy air for at least the third day.

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.

Air quality alerts have been issued across most of the Midwest, and hundreds of wildfires are burning across Canada.