Smoke from wildfires in Manitoba, a Western province facing its worst fire season in 30 years, has created hazardous air quality conditions across Eastern Canada and the United States.

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.

The Chicago area recorded ozone levels of 156 late Monday afternoon. Levels above 100 are considered unhealthy. Residents with respiratory issues, children and the elderly are advised to stay indoors and limit exposure to air outside until Tuesday evening.