Canadian wildfires in Manitoba and Saskatchewan have prompted air quality alerts in Minnesota, Wisconsin and Michigan on Wednesday and Thursday as residents are advised to "limit prolonged or heavy exertion.

It expires on Friday at midnight, due to elevated levels of fine particulate (PM2.5), the Department of Environment, Great Lakes, and Energy said.

Smoke from forest fires in the Prairies will affect southern Ontario Wednesday night, Environment Canada says. The statement came just as the weather agency lifted the city's fifth heat warning this year.