Maps: Wildfire smoke forecast for the Midwest and northern U.S.

Data GraphicsWhere the wildfire smoke from Canada is blowing, and how dangerous it isMore than 100 million people nationwide are under air quality alerts due to wildfire smoke.Listen to this article with a free profile00:0000:00Wildfire smoke from Canada shrouds the sun as it rises behind the skyline of midtown Manhattan in New York City on Friday as seen from Jersey City, N.J.Gary Hershorn / Getty ImagesShareAdd NBC News to GoogleJuly 17, 2026, 6:21 PM EDTBy Ashley MowreaderHot summer days are getting stuffier for more than 100 million people in the U.S. as wildfire smoke drifts south and imposes dangerous risks to their health.Subscribe to read this story ad-freeGet unlimited access to ad-free articles and exclusive content.Hundreds of wildfires burning in Canada have created a thick wave of smoke that’s shrouding swaths of the U.S. from Milwaukee to Washington, D.C., in unhealthy air. As of Thursday, more than 800 wildfires are actively burning across Canada, with large clusters in Ontario near the border with Minnesota. A heat wave across North America is trapping the unhealthy air and carrying it south.With smoky air comes certain health risks. The Environmental Protection Agency uses a measure called the Air Quality Index to assess how polluted the air is. Scores of 100 or more (out of 500) mean the air is unhealthy and could harm people’s health.Some U.S. cities — including Chicago, Detroit, Milwaukee, Pittsburgh and Washington — had ratings of more than 200 and led the world in rankings for worst air quality on Friday, according to data from air pollution monitoring company IQAir. Parts of Michigan, Ohio and Wisconsin had AQI ratings in the 300s on Friday afternoon — levels high enough that experts advise avoiding outdoor activities.In response, public health officials have issued air quality advisories and suspended some government operations. New York launched emergency operations Wednesday, offering free KN95 masks and opening shelter space. Due to deteri...