Smoke from Canadian wildfires is causing air quality concerns for millions of Americans in the Midwest and Northeast.

Smoke from ongoing wildfires across Canada continued to drift into parts of the United States on Wednesday, causing hazy skies and triggering air quality alerts in multiple states across the upper Midwest and Northeast.

Smoke from Canadian wildfires continues to affect air quality across the Midwest, though Monday’s conditions were an improvement for most of the Chicago area.