Smoke from wildfires burning in Canada is blowing into northeastern Minnesota, and it's making the air unhealthy to breathe.

The Minnesota Pollution Control Agency has issued an air quality alert in effect from 8 a.m. Thursday to 6 p.m. Friday for Lake, Cook, St. Louis and Carlton counties. Cities affected include Two Harbors, Silver Bay, Hibbing, Ely, Duluth, and the Tribal Nations of Grand Portage and Fond du Lac.

A second push of smoke from fires burning in Manitoba and Saskatchewan will be transported into Minnesota on Friday and may affect a larger area of the state, the MPCA said. Additional alerts may be issued, the agency said.

Thursday's warning means air will reach the unhealthy range, or red on the agency's five color-coded scale ranking air quality. Red is in the middle on the scale with yellow and orange below and purple and maroon above, signaling even worse air.

With the red alert, the air could look hazy and reduce visibility. The pollutants could cause anybody to experience symptoms such as irritated eyes, nose and throat, coughing, chest tightness or shortness of breath, the MPCA said.

People with conditions such as lung disease (including asthma), heart disease, COPD, and children and older adults, should avoid prolonged or heavy exertion, the National Weather Service said.

Both agencies ask the public to reduce or refrain as much as possible from activities that contribute to air pollution, including outdoor burning and reduce vehicle trips and idling.

The Weather Service also advises people to close windows to keep smoke from entering homes and businesses.