Thick plumes of smoke from Canadian wildfires are pouring into major cities across the Great Lakes, Northeast and Mid-Atlantic, bringing dangerous air quality to more than 100 million people.
Many people are wearing face masks to protect themselves from the polluted air, which will last through at least Saturday in some areas as new waves of smoke waft south.
In Canada, 3,500 fires have burned more than 6 million acres this summer, with a dozen blazes flaring up in Ontario in recent weeks. The smoke is streaming into the United States thanks to a record-breaking heat dome parked over the central part of the country.
