CHICAGO (WLS) — The Chicago area is under an air quality alert until Thursday due to the Canadian wildfire smoke until Thursday.

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The Illinois Environmental Protection Agency declared an “Air Pollution Action Day” for the greater Chicago area until midnight on Thursday.

Children, and those with pulmonary or respiratory diseases such as asthma, are recommended to limit their time outdoors.

The alert was in effect for northern and northeast Illinois and Northwest Indiana.

A tracker with the latest updates on air quality levels for areas across the state can be found on the AirNow government website.

The video in the player above is from a previous report.

Conditions at ground level are unhealthy in Midwest

The U.S. Environmental Protection Agency’s AirNow map showed a swath of red for “unhealthy” conditions across the eastern half Minnesota into western Wisconsin and northern Iowa. The map also showed purple for “very unhealthy” across much of the Minneapolis-St. Paul metropolitan area, where the Air Quality Index numbers of 250 and were common, though conditions started to improve slightly by late morning.

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.

The Canadian fire situation

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.

Winnipeg hotels opened Monday to evacuees. More than 17,000 Manitoba residents have been displaced since last week, including 5,000 residents of the community of Flin Flon, nearly 400 miles (645 kilometers) northwest of Winnipeg. In neighboring Saskatchewan, 2,500 residents of the town of La Ronge were ordered to flee Monday, on top of more than 8,000 in the province who had been evacuated earlier.

In Saskatoon, where the premiers of Canada’s provinces and the country’s prime minister met Monday, Saskatchewan Premier Scott Moe said all of Canada has come together to help the Prairie provinces.

Two people were killed by a wildfire in mid-May in Lac du Bonnet, northeast of Winnipeg.

Canada’s worst-ever wildfire season was in 2023. It choked much of North America with dangerous smoke for months.

AP News contributed to this report, including: Tammy Webber in Fenton, Michigan, and Scott McFetridge in Des Moines, Iowa.