Wildfire smoke drives hazardous air quality across US and Canada
Dense smoke from wildfires in Minnesota and Ontario has pushed air quality to unhealthy levels from the Great Lakes to the Northeast, prompting evacuations, park closures and health advisories.
Smoke from a series of wildfires in Minnesota and Ontario has spread across the Great Lakes region into the Northeast, raising the Air Quality Index to hazardous levels in many areas. The U.S. Environmental Protection Agency reported AQI readings above 500 in parts of the Midwest and over 750 in some locations on Isle Royale National Park. Officials in New York, Michigan, Ohio, Indiana and Minnesota have issued health alerts and advised residents to limit outdoor activity.
The Forest Service closed the Boundary Waters Canoe Area Wilderness on Tuesday, citing fire growth that has exceeded 14,000 acres, including the Thumb Fire that has crossed the border into Canada. Evacuation orders have been issued for Lake County, Minnesota, and 15 communities near Thunder Bay, Ontario, with additional evacuations under consideration.
"There are literally thousands of people who could be out there," said Margo Whitt, public information officer for Superior National Forest, referring to potential evacuees.
More than 150 fire crews and nearly 50 aircraft are fighting the blazes, according to Ontario Premier Doug Ford. The province has also requested federal assistance, including the possible deployment of Canadian soldiers for air evacuations.
"The situation is evolving and impacts to communities may continue to escalate rapidly," wrote Ontario Minister of Emergency Preparedness Jill Dunlop in a letter to federal authorities.
National parks in the region, including Voyageurs, Isle Royale and Indiana Dunes, have warned visitors of unhealthy air and limited programming. Isle Royale reported ash falling and AQI readings that far exceed the standard scale's maximum of 500.
Meteorologists attribute the smoke transport to a strong jet stream that has carried the plume eastward, while a persistent heat dome has maintained dry, windy conditions that favor fire spread. Climate scientists note that rising nighttime temperatures are extending the fire season and reducing the usual nighttime slowdown that helps firefighters contain flames.
"What we’re seeing here is a dramatic increase in wildfires in North America," said Jonathan Overpeck, climate scientist at the University of Michigan.
Air quality officials in Toronto rated the risk as "very high" and urged residents to stay indoors, with some outdoor facilities closed. The smoke is expected to disperse gradually as the jet stream shifts in the coming days, potentially improving conditions in the Midwest and Northeast.