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WILDFIRE SMOKE FROM CANADA CREATES HEALTH CONCERNS IN THE U.S.
Smoke from hundreds of wildfires burning across Canada has pushed air quality advisories from the Midwest to the Mid-Atlantic this week, affecting more than 100 million people
By Sigrid Vestergaard Frandsen, Director of Environmental Health
07/19/2026
Right now, wildfires are surging in southern and central Canada and parts of Minnesota. The smoke, rapidly spreading across the U.S., is creating unhealthy air quality, affecting more than 100 million people, and making Chicago’s air quality the worst in the world on Thursday evening, followed by Detroit and Minneapolis, according to IQAir’s global rankings.
As of Sunday, July 19th, Canada has 963 active wildfires across the country, with 139 remaining out of control. This covers an area of 2,915,578 hectares. To put that into perspective, an average of 1,908,247 hectares have been burnt across Canada in the last 25 years.
Map of Canadian wildfires as of July 19th, 2026. Source: Government of Canada
The smoke from the Canadian wildfires is travelling across country borders, blanketing more than 20 U.S. states and leaving cities throttled by the air quality.
Wildfire smoke is a mixture of hazardous air pollutants, such as particle matter (PM2.5), nitrogen oxides (NO2), ozone, aromatic hydrocarbons, and lead. In addition to contaminating the air with toxic pollutants, wildfires also impact the climate by releasing large quantities of carbon dioxide and other greenhouse gases into the atmosphere, warming the atmosphere even more, making way for more wildfires.
Smoke detection from Canadian wildfires as of July 19th, 2026.
Source: NOAA HMS Smoke Detection
The scale of the health impacts is evident in past events. During the widespread Canadian wildfire smoke episodes of 2023, asthma-related emergency room visits across the U.S. were 17% higher than average on the days smoke pushed air quality into "unhealthy" territory, with the largest increases among children and working-age adults.
In New York City alone, when PM2.5 levels spiked roughly elevenfold above normal during that same event, daily asthma ER visits jumped from an average of about 182 to 261. Some studies on pediatric emergency visits have found even sharper spikes, with wildfire-specific smoke linked to a rise in asthma-related visits from under 4% of cases to as much as 30% during heavy smoke periods.
This is a preview of what forecasters expect from this week's smoke as it settles over major population centers. The good news is that the vast majority of these visits are preventable with a few basic precautions: checking your local AQI before spending time outdoors, keeping windows closed on the worst days, and using an N95 mask if you have to be outside for long stretches in heavy smoke.
With climate change leading to warmer temperatures and drier conditions and the increasing urbanization of rural areas, the fire season is starting earlier and ending later. Wildfire events are getting more extreme in terms of acres burned, duration, and intensity, and they can disrupt transportation, communications, water supply, and power and gas services.
Smoke from Canadian wildfires blanketing Manhattan, NYC, 2023. Photo: Dr. Alexander More
This week's smoke will clear eventually — most forecasts show conditions improving by early next week as wind patterns shift. But with Canada's fire season running well above its 25-year average and climate trends pointing toward longer, more intense fire years ahead, this kind of cross-border smoke event is becoming less of an anomaly and more of a seasonal fixture. For now, the most useful thing anyone downwind can do is pay attention to their local air quality index and adjust their day accordingly — because on the worst days, the biggest risk isn't the fire itself. It's what's left floating in the air long after it.