Air quality worsens in eastern US as Canadian wildfire smoke hangs over Midwest
Jun 4, 2025, 9:23 AM | Updated: 1:16 pm
PORTLAND, Maine (AP) — Smoke from Canadian wildfires started making air quality worse in the eastern U.S. on Wednesday as several Midwestern states battled conditions deemed unhealthy by the federal government.
The fires have forced thousands of Canadians to flee their homes and sent smoke as far as Europe.
In the U.S., the Midwest is bearing the brunt. Smoke lingered on the skylines of cities from Kansas City to Minneapolis, and a swath of the region had unhealthy air quality Wednesday, according to an Environmental Protection Agency map.
Iowa issued a statewide air quality alert through early Thursday, urging residents to limit certain outdoor activities and warning of possible health effects due to the thick smoke. Wisconsin officials made similar suggestions as the smoke drifted southeast across the state.
In Michigan’s Upper Peninsula, authorities advised people shut windows at night, avoid strenuous activity outside and watch for breathing issues.
Parts of Maine, Vermont, New Hampshire and New York had areas of moderate air quality concern, and officials advised sensitive people to consider reducing outdoor activity.
New Hampshire authorities hoped conditions would improve by late Wednesday.
“The particle air pollution event is the result of extensive wildfires in central and western Canada,” the state’s Department of Environmental Services said. “Wind patterns are forecasted to transport plumes of smoke from these fires across much of New England and New Hampshire.”
The Minnesota Pollution Control Agency issued an alert for almost the entire state into Wednesday, but the Twin Cities area got the worst of it in the Midwest on Tuesday.
“As the smoke continues to move across the state Tuesday, air quality will slowly improve from northwest to southeast for the remainder of the alert area,” the agency said. “The smoke is expected to leave the state by Wednesday at noon.”
The Iowa Department of Natural Resources warned that air quality in a band from the state’s southwest corner to the northeast could fall into the unhealthy category through Thursday morning. The agency recommended that people, especially those with heart and lung disease, avoid long or intense activities and to take extra breaks while doing strenuous actions outdoors.
The U.S. Environmental Protection Agency’s AirNow map showed a swath of red for “unhealthy” conditions across Wisconsin and northern Iowa. Northern Michigan was also the site of many unhealthy zones, the agency said. The Air Quality Index was around 160 in many parts of the upper Midwest, indicating unhealthy conditions.
The Air Quality Index — AQI — measures how clean or polluted the air is, focusing on health effects that might be experienced within a few hours or days after breathing polluted air. It is based on ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide. Particulates are the main issue from the fires
The index ranges from green, where the air quality is satisfactory and air pollution poses little or no risk, to maroon, which is considered hazardous. That level comes with health warnings of emergency conditions where everyone is more likely to be affected, according to AirNow.
There were areas of reduced air quality all over the U.S. on Wednesday, with numerous advisories about moderate air quality concerns as far away as Kansas and Georgia.
Canada is having another bad wildfire season. Most of the smoke reaching the American Midwest has been coming from fires northwest of the provincial capital of Winnipeg in Manitoba.
Canada’s worst-ever wildfire season was in 2023. It choked much of North America with dangerous smoke for months.
Canada’s wildfires are so large and intense that the smoke is even reaching Europe, where it is causing hazy skies but isn’t expected to affect surface-air quality, according the European climate service Copernicus.
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Karnowski reported from Minneapolis. Associated Press writers Jack Dura in Bismarck, North Dakota; Kathy McCormack in Concord, New Hampshire; Tammy Webber in Fenton, Michigan; and Scott McFetridge in Des Moines, Iowa, contributed to this report.
