Maps show wildfire smoke forecast, air quality alerts due to pollution from Canadian, Minnesota fires

Heavy smoke from wildfires blazing in Canada and Minnesota is engulfing large swaths of the Midwest and Northeast U.S. this week, impacting air quality as millions of people are exposed to hazardous levels of air pollution. More than 100 wildfires are burning in Canada, and winds are carrying the smoke southeast. Multiple wildfires are raging in northern Minnesota. Detroit, Minneapolis and Chicago ranked among the top five most polluted major cities in the world on Thursday, as air quality alerts stretched from Minnesota to parts of the Northeast. The entire state of Michigan was under an air quality alert Thursday. An air quality advisory was in effect Thursday for all of New York state, and officials said N95-style masks would be distributed to commuters in New York City. Pennsylvania declared a Code Red air quality alert for Thursday. Air quality emergencies impact at least 21 states amid wildfires. Dan Westervelt, associate professor at Columbia University's Climate School, said severe drought conditions combined with heat in Canada and the U.S. have created "a perfect storm for really dry conditions to provide a lot of fuel for these wildfires to burn." Research shows warming temperatures from burning coal, oil and gas are making fires more frequent and intense. A dramatic video captured the moment a freight train near Armstrong, Ontario, was suddenly surrounded by a wall of burning trees earlier this week. "This could potentially overtake us here, this has gotten a little scary," one crew member said in the video. The Canadian National Railway later suspended rail operations there, but said everyone on board the train got through safely. Long term, exposure to fine particulate matter from wildfire smoke is one of the leading causes of premature death.