Hundreds of wildfires still burning in Canada are expected to undermine air quality across the Upper Midwest and Northeast into Tuesday.

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 has sent a blanket of smoke over the midwestern United States this weekend. The National Weather Service (NWS) has issued air quality alerts for Minnesota and Wisconsin, as well as, Iowa, Illinois Michigan, and parts of Nebraska and Missouri.