Smoke from Canadian wildfires continues to affect air quality across the Midwest, though Monday’s conditions were an improvement for most of the Chicago area.

An Illinois Air Pollution Action Day is declared when weather conditions are such that widespread ozone and or particulate levels are expected to be at or above the Unhealthy for Sensitive Groups (USG) category of the Air Quality Index for all or almost all of Illinois.

Health officials from Minnesota to Maine have issued alerts warning of poor air quality from wildfires burning in Canada. People are advised to limit outdoor exposure.