The EPA's Air Quality Index can tell you whether breathing outside air can be harmful. Here's how to read the scale to plan accordingly in Michigan.

Chicago's air quality alert continues due to Canadian wildfires, affecting sensitive groups and prompting health advisories.

Chicago faces a heat wave with poor air quality due to wildfire smoke and ozone; temperatures may hit mid-90s.

The Illinois EPA declared an Air Pollution Action Day in the Chicago metro area. See today's air quality index forecast for Illinois.

The Air Quality Index (AQI) is a national system developed by the U.S. Environmental Protection Agency (EPA) to translate various air pollutant concentrations into a single, easy-to-understand number.

The alert comes as humidity is expected to increase Tuesday, with high temperatures in the mid 80s to low 90s, with heat indices reaching 100 by Wednesday.

Low: 68.   Tuesday opens with plenty of sunshine but some cottony cumulus clouds arrive on the scene by/during the ...

The Chicago area recorded ozone levels of 156 late Monday afternoon. Levels above 100 are considered unhealthy. Residents ...

The Illinois Environmental Protection Agency has issued an Air Pollution Action Day for Tuesday, July 15. Here's what to know ...

Unhealthy air has invaded Minnesota, Wisconsin and North Dakota early this week as a new round of wildfire smoke from Canada ...

Air quality across Minnesota was pretty bad this past weekend. It was so bad that it was ranked as some of the worst in the ...