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

Air quality alerts have been issued across most of the Midwest, and hundreds of wildfires are burning across Canada.

Wildfire smoke from Canada and the western US has drifted over the Great Lakes, causing hazardous air quality in Chicago, Minneapolis, and Green Bay. Fine particles in the smoke pose health risks, especially for vulnerable groups,