Millions of Americans are on alert for unhealthy air quality as smoke from wildfires in neighboring Canada drifts to the United States.
Wildfires have burned a record of 20 million acres across Canada so far this year, with no end in sight. There are currently 500 active wildfires throughout the country and more than 250 have been deemed out of control, according to the Canadian Interagency Forest Fire Center. The smoke has been making its way to the U.S. for over a month.