Millions Under Air Quality Alerts as Canadian Wildfire Smoke Chokes the Northeast

Massive plumes of wildfire smoke are settling over parts of Canada and the northeastern and midwestern United States, pushing air quality to unhealthy levels in cities including Boston and Toronto, and conditions could worsen before they improve.

More than 800 wildfires are currently burning across Canada, with dozens out of control in western Ontario, the source of most of the smoke choking the region. Air quality alerts have been issued from Wisconsin and Michigan through New York and Massachusetts.

Toronto recorded some of the worst air quality in North America, with the AQI reaching 220, or "very unhealthy," Wednesday morning. Boston's AQI hit 147, in the "unhealthy" range, with little improvement expected heading into Thursday.

"In 2023, a major fire outbreak in Quebec caused days of unhealthy air quality in the northeastern U.S.," said Dan DePodwin, AccuWeather's vice president of forecast operations. "This event could cause similar levels of poor air quality in spots."

The smoke is expected to spread even further as the week goes on. Meteorologists said that dense smoke coverage will become more expansive on Thursday, blanketing much of the Great Lakes and New England, including Detroit, Cleveland, New York and Philadelphia, with hazy skies stretching across much of the northern U.S.