Smoke-Filled Skies Leave Midwest Fearing Another Season of Polluted Air

A cloud of smoke from Canadian wildfires suddenly blanketed Minnesota on Sunday evening, marring what had otherwise been a sun-drenched weekend and leaving some residents wondering whether the misery of last summer was starting all over again.

A thick haze of smoke had repeatedly hung over cities in the Midwest and on the East Coast throughout the summer last year, leaving some communities breathing air so polluted that schools were closed and sporting events canceled.

For now, experts say that a similar pattern has indeed appeared to have emerged. “We’re expecting a pretty active wildfire season in Canada,” said David Brown, an air quality meteorologist at the Minnesota Pollution Control Agency. “But we don’t think it will be quite as extreme.”

Mr. Brown said a key difference was that drought conditions in Canada were not as extensive as they were last year, when fires raged in the provinces of Quebec and Ontario. For now, he added, people on the East Coast appear unlikely to endure the kind of periods of highly polluted air that startled many people last year.

Air pollution from wildfires in the northern regions of the United States has worsened over the past decade as a result of warming temperatures and drought, experts said. Periods of poor air quality can be particularly dangerous for toddlers, older people and those with respiratory and cardiovascular conditions.

“Unfortunately, it seems like these events are becoming more and more common,” said Jesse Berman, an environmental epidemiologist at the University of Minnesota. “We need to be aware of it and adapt to the reality that smoke will blanket parts of the state during the summer.”