Wildfire Smoke Temporarily Worsens Air Quality in Midwest and Northeast Cities

Smoke from hundreds of wildfires burning in Canada and additional fires in northern Minnesota reached the U.S. Midwest and Northeast on July 16 and 17, producing hazardous air quality in several major cities. Northwest winds carried the smoke across the Great Lakes and into the Northeast during the week ending July 17, creating yellow and hazy skies and reducing visibility.

Chicago, Detroit, Minneapolis, and New York ranked among the cities reporting some of the worst air quality levels in the world on July 16, according to monitoring company IQAir. The National Weather Service said air quality alerts remained in effect on July 17 in parts of Minnesota, Wisconsin, Michigan, Illinois, Indiana, Ohio, West Virginia, Pennsylvania, New York, Vermont, New Jersey, Delaware, Maryland, Virginia, and the Carolinas.

On July 16, smoke levels were dangerous across Minnesota, Michigan, northern Illinois, northern Ohio, and into Ontario, with hazardous readings in Minneapolis, Milwaukee, and Toronto.

The Minnesota Pollution Control Agency reported that PM2.5 concentrations in parts of northeastern Minnesota peaked near 900 micrograms per cubic meter on July 16. The agency issued an air quality alert through July 17 for east-central, central, west-central, southeast, north-central, northwest, and northeast Minnesota.

"Heavy smoke will continue to disperse and retreat to the north this evening into Friday morning, with improvements in air quality from south to north with time," the agency said.

Nearly 900 wildfires are burning across Canada, with over 200 considered out of control, according to the Canadian Wildland Fire Information System. Most of the fires were in the central provinces of Manitoba, Ontario, and Saskatchewan. Multiple fires remained active in Minnesota, including six large fires that have scorched more than 41,000 acres as of July 16, the National Interagency Fire Center said.

The Minnesota Incident Command System reported 15 active wildfires in the Superior National Forest as of July 17, with three inside the Boundary Waters Canoe Area Wilderness. In New York, local officials urged residents to limit outdoor time and cautioned older adults, pregnant people, and people with heart and lung disease to remain inside.