Chicago had the worst air quality overnight Wednesday into Thursday, the latest American city to feel the impact of wildfire smoke drifting south from Canada, as states across the Upper Midwest, Great Lakes and Northeast are covered in Air Quality alerts.

Smoke from Canadian wildfires is beginning to worsen air quality in the eastern U.S. as several Midwestern states battle conditions deemed unhealthy by the federal government

Smoke from Canadian wildfires is engulfing much of the eastern and central United States and and is expected to continue for days.