Canadian Wildfire Smoke Spreads Across U.S., Worsens Air Quality

Smoke from massive wildfires burning across Canada drifted into the United States this week, reducing air quality across parts of the Midwest, Great Lakes and Northeast as authorities issued health advisories for millions of people. Dense smoke from fires in northern Ontario and western Canada covered cities including Toronto, where air pollution ranked among the worst in the world on Wednesday, while haze spread into states including Minnesota, Michigan, Wisconsin, New York and parts of New England. Forecasters warned that shifting winds could carry smoke farther south and east through the end of the week.

The fires have also forced evacuations in parts of Canada and northern Minnesota, where lightning-sparked blazes led officials to close portions of the Boundary Waters Canoe Area Wilderness and remove thousands of campers from remote areas. Canadian authorities reported hundreds of active wildfires nationwide, with more than 100 considered out of control. The combination of wildfire smoke and unusually hot temperatures has increased health concerns, particularly for older adults, children and people with heart or lung conditions, as officials advised limiting prolonged outdoor exposure and keeping indoor air as clean as possible.