Smoke from the more than 700 wildfires burning in Canada is continuing to blanket parts of the Midwest for a final day.

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.

“Air quality and visibility due to wildfire smoke can fluctuate over short distances and can vary considerably from hour to hour,” Environment and Climate Change Canada (ECCC) said in its statement.