Health officials are urging caution as smoke and heat arrive together this week.
Heavy smoke from large wildfires burning in Canada and Minnesota is spreading into the Midwest and Northeast this week, threatening unhealthy air quality for roughly 100 million people through Friday. A heat dome sitting over the middle of the country is helping push the smoke into the lower atmosphere and trapping it closer to the ground, worsening conditions even as temperatures climb toward 100 degrees in some areas.
Where the smoke is worst right now
Minnesota has been hit hardest so far. State officials issued an air quality alert running from Tuesday through Friday covering the Twin Cities metro area, Alexandria and Two Harbors, with the heaviest smoke concentrated in the northeastern part of the state. Conditions in Two Harbors and the Grand Portage Tribal Nation were expected to reach hazardous levels, unsafe for the general public rather than only those with existing health conditions.
A heat dome is making things worse
Meteorologists say the timing could hardly be worse. A large area of high pressure parked over the central United States, visible on satellite as a clear patch of sky with air circulating around it, is both driving temperatures into the high 90s and low 100s and pinning wildfire smoke near the surface rather than letting it disperse higher in the atmosphere. Forecasters have warned that the combination of extreme heat is particularly dangerous, since both conditions push people to want to stay indoors for different but overlapping reasons.
How far the smoke will travel
By Wednesday afternoon, forecasters expected intense smoke to reach the East Coast and Midwest, including the New England coastline, northern Pennsylvania, Detroit and Milwaukee. The National Weather Service office covering the Philadelphia and South Jersey region said smoke that had been lingering high in the atmosphere would begin dropping closer to the ground Wednesday evening and into Thursday, reaching a level where it becomes noticeable by smell and can reduce visibility. Multiple counties in western and central New York were placed under an air quality advisory through midnight Wednesday, and forecasters said the most concentrated smoke could push as far south as Washington, D.C., by midday Thursday. In parts of Maine, residents reported skies turning a yellowish or brownish tint as smoke moved through ahead of an approaching cold front. New York City officials also warned that Wednesday’s air quality could deteriorate, though they said the worst case forecasts remain well short of the extreme spike the city saw in 2023, when Canadian wildfire smoke pushed its air quality index into dangerous territory.
Why this keeps happening
Researchers point to a familiar combination behind this year’s fires: severe drought paired with unusually hot conditions across Canada and the northern United States, creating abundant dry fuel for wildfires to spread quickly. Climate scientists have said that warming driven by the continued burning of coal, oil and gas is making wildfires more frequent and more intense over time, a trend that has repeatedly sent smoke drifting into major U.S. population centers in recent years.
How to protect yourself
Health officials recommend limiting time outdoors as much as possible while both the heat and the smoke persist, particularly for children, older adults and anyone with existing heart or lung conditions. Wearing an N95 mask outdoors, keeping windows closed and running an air purifier or air conditioner indoors can help reduce exposure. Fine particle pollution from wildfire smoke can trigger shortness of breath, coughing, dizziness and fatigue, and worsen chronic heart and lung disease. Long term exposure to this kind of pollution remains one of the leading environmental contributors to premature death in the United States.
