These two U.S. cities are among the most polluted in the world because of Canadian wildfire smoke

Air pollution shrouds the city of Chicago on July 31, 2025. (ElegantDivasHusband via Storyful)

Canadian wildfire smoke has ignited air quality alerts in the Midwest U.S., causing Chicago and Minneapolis to be among the world’s most polluted major cities.

Computer models and satellites show the smoke originated from Saskatchewan, Manitoba and far eastern Alberta, Ed Shimon, a warning co-ordination meteorologist with the National Weather Service in the U.S., told CTV News Winnipeg on Thursday.

Eastern North Dakota, Minnesota, Wisconsin, Illinois and Iowa had cloudy conditions partly because of the Canadian wildfires, Shimon said.

Chicago and Minneapolis are the only cities in North America that have made the top 10 list Friday published by IQAir, a Swiss real-time air quality monitoring platform. Minneapolis was No. 2 followed by Chicago as of 9:30 a.m. ET. Kinshasa, the capital of the Democratic Republic of the Congo, topped the list.

Footage posted by @ElegantDivasHusband on X on Thursday shows smoke so thick that Chicago’s buildings are barely visible. The footage and news of the wildfire ranking was reported by Storyful.

Brian Urbaszewski, director of environmental health programs at the Respiratory Health Association, was quoted as saying in the Chicago Sun-Times on Thursday that the air quality was so “dangerous” that some people may need to go to the emergency room and could die.

Chicago was the most polluted in the world for a few hours midday Thursday based on the IQAir ranking, the Chicago Sun-Times reported. Minneapolis was No. 3, followed by Detroit. The U.S. publication reported the smoke stemmed from Canadian wildfires.

“We’re over a thousands miles away, and we’re breathing all this smoke. It’s just off the charts,” Urbaszewski told the publication.

With files from CTV News Winnipeg’s Milan Lukes