The hazy skies in the Chicago area are the visible sign of the poor air quality Thursday as smoke from Canadian wildfires drifts into our area.

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.

Wildfire smoke from Canada turned Chicago into one of the world’s most polluted metro areas as the Lollapalooza music festival began.