Science & Nature
‘Unhealthy’ Air Quality Alert in Chicago Extended Through Friday Night, as Canadian Wildfire Smoke Lingers
The Willis Tower is pictured in downtown Chicago, where the air quality has been categorized "unhealthy" by the U.S. Environmental Protection Agency, on June 27, 2023. (AP Photo / Claire Savage, file)
Wildfire smoke from Canada continues to create unhealthy air conditions in the Chicago region, with environmental officials extending an “action day” alert through midnight Friday.
On Thursday, the wildfire smoke sunk to the surface atmosphere and was expected to linger there Friday across northern Illinois and along the Lake Michigan shoreline, according to the Illinois Environmental Protection Agency.
The high levels of pollution prompted the agency to declare an “action day,” the first of 2025.
Thursday's air quality pushed into the “red” zone of the EPA's Air Quality Index, meaning pollution levels were unhealthy for older adults, children, teens and people with heart or lung disease.
Friday's air is expected to hit the “orange” level of the index, meaning pollution levels could create health concerns for people sensitive to air pollution.
People should consider limiting or postponing prolonged outdoor activity, the National Weather Service said.
Possible health issues could include wheezing, coughing, a fast heartbeat, fatigue, chest pain and shortness of breath, according to officials.
Unhealthy air quality due to Canadian wildfire smoke to persist through Fri night. Consider limiting or postponing prolonged outdoor activity.
Up-to-date air quality information here:#ILwx: https://t.co/W27QkDoHeG#INwx: https://t.co/JHE99nPd35 & https://t.co/jACfvaAA1e pic.twitter.com/ytmWG9XUou— NWS Chicago (@NWSChicago) June 5, 2025
The Air Quality Index 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.
It’s been nearly two years since smoke from Canadian wildfires darkened the city’s skies and prompted air quality warnings that sent most people indoors.
Canada is having another bad wildfire season, and more than 27,000 people in three provinces have been forced to evacuate. Most of the smoke reaching the American Midwest has been coming from fires northwest of the provincial capital of Winnipeg in Manitoba.
Smoky conditions that have reached the U.S. periodically in recent weeks extended as far east this week as Michigan, west into the Dakotas and Nebraska, and as far to the southeast as Georgia.
In Illinois, the highest concentrations of Canadian wildfire smoke at the surface are expected across the northern third of the state, though officials noted that forecast models have so far tended to “underpredict” the amount of smoke reaching central Illinois.
State officials are encouraging businesses and residents in the area to try and reduce contributions to air pollution, particularly on action days, by limiting driving or idling vehicles; conserving energy usage; and avoiding the use of gasoline-powered equipment.
Patty Wetli and The Associated Press contributed to this report.
