Wildfire Smoke from Canada and Minnesota Impacts Air Quality Across U.S. Midwest and Northeast

Heavy wildfire smoke from fires burning primarily in Canada and northern Minnesota spread across the United States on Thursday, darkening skies from the Great Lakes to the East Coast and reducing visibility to as little as half a mile in some areas. A high-pressure system has trapped the smoke near the ground, according to Steven Freitag, a National Weather Service meteorologist in Detroit, where air quality ranked among the worst for major cities worldwide.

Air-quality alerts ranging from "unhealthy" to "hazardous" were issued for all of Michigan, much of Minnesota and the Chicago area. National Weather Service meteorologist Jake Petr warned that even if northwest winds clear the skies later in the week, smoke could return until the fires are extinguished, which may not occur until snowfall arrives in the affected regions.

In New York City, a thick orange-yellow haze prompted the opening of cooling centers and the distribution of tens of thousands of masks at transit hubs. City officials moved school and park activities indoors and advised residents to limit strenuous outdoor exertion. Similar recommendations were issued in Philadelphia, where public health commissioner Dr. Palak Raval-Nelson urged people to stay inside or wear N95/KN95 masks.

Local residents described the conditions: Omar Mitchell, a Detroit restaurateur, said the smoke “is scary” and expressed concern about potential long-term health effects. Bill Ostrowski, a senior citizen walking downtown Chicago, noted the unpleasant odor and visibility of smoke-shrouded skyscrapers. In St. Paul, Minnesota, Brent Williams of the University of Minnesota’s soil, water and climate department said the sky appeared “glowing yellow” and warned that weeks to months of intermittent smoke are possible.

Health experts highlighted that microscopic particles in wildfire smoke can penetrate deep into the lungs and enter the bloodstream, increasing the risk of heart, lung, cardiovascular and neurological problems, and contributing to premature deaths. A recent study estimated that long-term exposure to such particles accounts for roughly 24,100 deaths annually in the contiguous United States.

In Minnesota, fire crews continued search operations in remote wilderness areas, and the Boundary Waters were closed after an estimated 6,000-10,000 visitors were present. Karen Harrison, a spokesperson for state and federal agencies, said smoke was hampering helicopter operations and that fires are expected to persist until fall, with some burning until snow cover arrives. The Royal Canadian Air Force evacuated 11 teenagers and four staff members from a wildfire-affected Ontario park near the Minnesota border.

Meteorologists noted that the smoke plume could thicken again later in the day and might shift southward before potentially returning overnight, suggesting that air-quality concerns could linger for the remainder of the week.