Canadian wildfire smoke blowing down into Maine prompted the Maine Department of Environmental Protection to issue an alert for poor air quality in northern and western Maine through Monday.

The DEP deemed the air quality “unhealthy” for the northern region, including the counties of Aroostook, Piscataquis, Penobscot and Somerset counties, on Sunday. The DEP forecast the air quality across the state to be “moderate” on Monday as changing winds shift the direction of the smoke.

Under unhealthy air quality conditions, people with heart or lung disease, older adults and children should avoid intense exertion altogether and should consider moving outdoor activities inside. Everyone else should reduce intense exercise and take more breaks in outdoor activities, according to the DEP.

For the western regions of the state, the DEP deemed the air quality “unhealthy for sensitive groups” on Sunday.

The air pollution comes from Canadian wildfires in Western Ontario, Manitoba, and into Northern Alberta and Saskatchewan, said Jon Palmer, a meteorologist at the National Weather Service office in Gray.

“I think people can still expect to see a good amount of haze and smoke across the area through the rest of this afternoon into tomorrow,”  Palmer said Sunday afternoon.

The air quality alert is in effect until 11 p.m. Monday. The New Hampshire Department of Environmental Services also issued an air quality alert.

Staff Writer Gillian Graham contributed.