Millions in the United States are facing another day of hazy skies fueled by hundreds of smoky wildfires burning across North America, impacting air quality in parts of the U.S. and raising health concerns.

Air quality alerts are now in place for 10 states from Minnesota to Connecticut and, on Tuesday afternoon, Boston is expected to see a nice break from the smoke thanks to onshore winds keeping smoke inland as Detroit and New York City may catch more of a break due to winds from the east as well.

Canada is battling more than 700 active wildfires across the country, roughly two-thirds of which are burning out of control, according to the Canadian Interagency Forest Fire Center (CIFFC). Smoke billowing from the blazes has blanketed central Canada and the northern U.S., prompting widespread air quality alerts.