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

Wildfire smoke drifting across the Great Lakes has caused air quality to plunge to hazardous levels in several states, affecting millions of people in major cities.

As has been the case much of the summer, the smoke invasion is targeting the Upper Midwest to Great Lakes. Beyond Thursday, smoke may impact more of the Northeast U.S. through and beyond Friday.