Heavy smoke from the Canadian wildfires is flowing across the border into the United States, creating hazardous air quality for more than 100 million people in the Midwest and Northeast.
Fires in the state have burned more than 3.6 million acres, mostly in the western half of the country, and smoke has already been a problem in parts of the West, Plains and Midwest this summer. But thicker smoke is expected to move over New York, Washington, D.C., and other eastern cities, driven by wildfires to the north.
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More than 3,000 fires have burned about 4.5 million acres in Canada this summer, and more than a dozen fires have started in Ontario in recent weeks, filling the skies with smoke similar to extreme conditions in 2023 and starting to drift south.
This year’s wildfire activity in Canada is nowhere near the intensity seen in 2023, but the combination of wildfires in Ontario and heat domes in the central United States are causing smoky troubles for millions of people.
Fossil fuel pollution that causes global warming raises the possibility of an extended smoke season, suggesting that extreme wildfire seasons like 2023, the worst season in Canadian history, may not remain an anomaly for long.
Unhealthy smoke heads toward Great Lakes and Northeast
The first smoke is already wafting across a wide area from Chicago to Boston. Most of this smoke remains high in the atmosphere, meaning it is not rapidly reducing air quality or posing a significant health risk.
But changes in weather patterns over the next few days could cause smoke to linger and additional plumes to sink to the surface Wednesday and Thursday, leading to unhealthy air quality from the upper Midwest to New England.
Do you smell smoke this morning? The cause is the outbreak of wildfires in Ontario. There should not be a significant impact on air quality today, but increased surface smoke could reduce visibility and air quality Wednesday through Thursday. High temperatures may also be restricted. pic.twitter.com/6QdV5965nt
— NWS New York New York (@NWSNewYorkNY) July 14, 2026
Wildfire smoke contains dangerous micropollutants called PM2.5 that can travel deep into your lungs or enter your bloodstream when inhaled. Ultrafine particles can cause breathing problems such as bronchitis and inflammation that can worsen diabetes, heart disease, and other health conditions.
Many areas in Michigan, Minnesota and Wisconsin are under smoke air quality warnings for the next few days, and the National Weather Service warned that smoke air quality concerns could also occur in Chicago later this week.
People with lung or heart disease, children, and the elderly are especially at risk of smoking-related illnesses. The NWS advises people to limit outdoor activities, close windows at night and avoid smoking.
The only hope the smoke brings is that it can provide some relief from the heat. That would be welcome news for many parts of the Northeast, where high temperatures are expected over the next few days as the smoke blocks sunlight.
This smoke is now flowing into the United States thanks to a record-breaking hot dome installed over the central part of the country.
So far this year, we’ve seen several heat domes, large, slow-moving areas of high pressure, form from the West Coast to the Northeast. Air moves clockwise around these domes, but so far none of the domes have been in the best position to pull Canadian smoke south.
The northern edge of this week’s heat dome is perfectly located in northern Minnesota and southern Ontario, where wildfires are raging. This alignment means smoke will flow east and south, directly into parts of the Midwest and Northeast.
With several months left of wildfire season, the door will remain open for more Canadian smoke to move south.
At this time three years ago, records were being broken, with 4,300 fires already burning 25 million acres across Canada.
In June 2023, northerly winds pushed a wall of wildfire smoke from Quebec into the Big Apple, and the smoke burned the New York City skyline.
The cause was a prevailing high pressure system over Hudson Bay and a storm system over Atlantic Canada. They worked together to send smoke into the Midwest and Northeast.
Both systems were stalled, and the smoke remained in place for about four days.
Smoke incidents in 2023 were so widespread that last year’s study estimated that more than 350 million people were exposed to air pollution from wildfire smoke every day.
Fortunately, wildfire activity in Canada started later than in record years, making it unlikely that this year’s smoke will be as widespread.
In the United States, fire seasons in the West are becoming longer and more extreme, increasing the likelihood of unhealthy wildfire smoke.
It turns out that much of the increase in surface wildfire smoke is due to climate change. The smoke eroded decades of air quality improvements in parts of the United States, especially in the West.
Pollution from global warming caused about 15,000 more deaths from wildfire particulate matter in the United States between 2006 and 2020 than would have occurred in a cooler world, a study published last year found.
