The return of wildfire smoke from fires burning in Canada has sparked another air quality alert in Minnesota, which will be in effect through Tuesday. The Minnesota Pollution Control Agency has placed the northern two-thirds of the state in the red alert zone, which means "unhealthy" for all residents, through 9 a.m. Tuesday.

Heavy surface smoke from wildfires in Canada is drifting across Minnesota on Monday, with unhealthy air quality levels expected in parts of the state.

As Canada grapples with one of its worst wildfire seasons on record, smoke from the blazes have prompted air quality alerts across the U.S.