Canadian wildfire smoke lingers, choking Midwest and Northeast air quality

Detroit, Chicago and Washington, D.C. were among the U.S. cities with the worst air on Friday as smoke from Canadian wildfires streamed south again. The haze was expected to linger through the weekend, with the Upper Midwest set to take the longest hit.

Dangerous air quality from the smoke affected more than 100 million people across the Midwest and Northeast as thick plumes pushed into major cities including New York, Minneapolis and Toronto. Some easing was expected in the East over the weekend, but the smoke was concentrated over the Upper Midwest, where some cities recorded extremely high pollution indexes on Thursday.

Chicago’s air quality alert was extended through Saturday night, with unhealthy levels tied to smoke from Canadian fires. Michigan’s Department of Environment, Great Lakes, and Energy said statewide air quality was being impacted by wildfire smoke, and officials across Maryland issued alerts as the plume spread through the Mid-Atlantic. In several cities, residents were urged to stay indoors, limit outdoor exposure and consider wearing N95 masks if they had to be outside.

The U.S. Environmental Protection Agency says wildfire smoke is largely made up of fine particulate matter, or PM2.5, which can harm healthy people and poses greater danger for children, older adults and people with heart or lung disease. Smoke was darkening skies from the Great Lakes to parts of the East Coast and cutting visibility in some places.

In 2023, smoke from more than 1,000 Canadian wildfires blanketed northern U.S. cities.