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 widespread Canadian wildfires has spread into the US, particularly affecting the Midwest and Northeast, leading to hazy conditions.

Health officials from Minnesota to Maine have issued alerts warning of poor air quality from wildfires burning in Canada. People are advised to limit outdoor exposure.