Maps: Canada wildfire smoke has covered the U.S. for more than a month

While tens of millions of people on the East Coast experienced their first bout with poor air quality Tuesday, due to wildfires burning in Canada, data shows that much of the United States has been dealing with the smoke of a string of northern fires since early May. Smoke from Canada’s wildfires blew into the United States this week, bringing hazy skies and unhealthy air stretching from New Hampshire to South Carolina. But smoke data from the National Oceanic and Atmospheric Administration shows that hazy air crossed most of the...