Smoke from active wildfires in south-central Canada and Minnesota has drifted across a large portion of the United States, triggering air quality alerts in more than 20 states.
Millions of Americans are bracing for unhealthy atmospheric conditions this week as winds carry dense plumes southward.
The smoke originates from over 180 active blazes in northern Ontario, which recently degraded Toronto's air quality to some of the worst levels globally.
NASA reported that atmospheric winds carried the smoke primarily southeast, spanning southern Ontario, Quebec, the US Midwest, and the Northeast.
Unhealthy to Hazardous Levels
According to the US Environmental Protection Agency, air quality reached "unhealthy" levels on Thursday morning in parts of New York, New Jersey, Pennsylvania, Delaware, Ohio, and Michigan.
Conditions deteriorated to "very unhealthy" in regions of Illinois, Wisconsin, Michigan, and Ohio, while areas of Minnesota, Wisconsin, and Detroit registered "hazardous" levels.
By Thursday morning, Detroit topped IQAir's global rankings for worst air quality, followed by Toronto, Minneapolis, and Chicago.
The National Weather Service in Detroit cautioned that smoke density would peak Thursday afternoon and night, significantly reducing visibility.
In response, New York City officials expanded emergency heat operations and opened hundreds of cooling centers to protect residents from combined high temperatures and smoke.
"It's dangerously hot and smoke from Canadian wildfires has worsened our air quality, which means New Yorkers need to be extra vigilant to stay safe," said Mayor Zohran Mamdani.
Governor Kathy Hochul announced the distribution of over 100,000 N95-style masks to affected counties, with additional masks provided to commuters at Penn Station and Grand Central.
Local officials warned this could be the most significant smoke event for New York City since 2023, when wildfire smoke blanketed the area in a dense orange haze.
Meteorologists confirmed that smoke would continue to impair visibility and health standards through Thursday evening, keeping alerts active until midnight.
In Boston, forecasters warned of smoky skies and reduced air quality, drawing concern from state leadership.
"With a record El Niño forecast for this year, we are looking at more wildfire smoke days ahead," said Senator Ed Markey.
"The climate crisis is here and it does not stop at our borders. Stay safe, Massachusetts."
The smoky conditions are projected to linger, with forecasters in Virginia and Ohio warning that additional waves of wildfire smoke will continue to drift south through Friday and into the weekend.
