Hundreds of wildfires burning in Canada are undermining U.S. air quality across the Upper Midwest and Northeast, making skies hazy from Detroit to New York City and even prompting a ground stop at Boston's Logan International Airport due to "low visibility."
At least 742 wildfires are currently burning in Canada, including 15 that ignited on Sunday, according to the Canadian Interagency Forest Fire Centre. At least 201 of the blazes remain out of control.
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