Minnesota is experiencing its longest air quality alert on record — seven days. The alert will remain in effect until noon on Monday, Aug. 4. It’s the result of Canada’s second most severe fire season yet.

Smoke from wildfires blazing across Canada is once again wafting over huge portions of the U.S. Midwest and worsening air quality there. On August 1 conditions are particularly bad in Minnesota, Iowa and Illinois.

Smoke from Canadian wildfires hovered over several Midwestern states Saturday, bringing warnings of unhealthy air.