A Week of Smoky Skies Across North America

NASA News 22 Jul 2026 2 min read

AI Insight

In July 2026, increased wildland fire activity in Canada, particularly in Ontario, produced extensive smoke plumes that traveled across North America, significantly degrading air quality from southern Canada through the U.S. Upper Midwest, Northeast, and Great Lakes regions. NASA's GEOS model tracked brown carbon aerosols—organic particles that contribute to PM2.5 pollution and appear as yellow, orange, and brown tints in smoke—showing how winds carried these emissions southeast over a week-long period from July 14-20. Major cities including Detroit, Toronto, Chicago, New York City, and Washington D.C. experienced air quality levels ranging from unhealthy to hazardous during this event.

Why it matters

This type of smoke contains PM2.5 particles that can aggravate cardiovascular and respiratory conditions in affected populations. The improved GEOS model capability to distinguish between wildfire-generated brown carbon and human-source pollution allows for more accurate tracking of smoke plumes and better public health warnings during wildfire events.

Confidence

7/10Peer-reviewedAstronomy & Space

Understand the Science

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Wildland fire activity in Canada ramped up in July 2026, a time of year when lightning ignitions typically increase, according to a seasonal outlook published by several North American fire agencies. The blazes sent smoke plumes pouring across the U.S. and Canada, affecting air quality in both countries.

This animation tracks brown carbon, the organic aerosols emitted by fires that give smoke plumes their characteristic yellow, orange, and brown tint. Brown carbon is a major component of a fire’s PM_2.5 emissions, a type of air pollution that can aggravate cardiovascular and respiratory conditions. Here, the plume drifts across North American skies from July 14 through July 20, 2026.

Data for the animation come from a version of the GEOS (Goddard Earth Observing System) model, which assimilates data from satellites, aircraft, and ground-based observing systems. In addition to satellite observations of aerosols and fires, the model also incorporates meteorological data such as air temperature, moisture, and winds to project the plume’s behavior.

On July 14, at the start of the animation, numerous fires had already cropped up, including more than 180 in Ontario and several in northern Minnesota. Winds carried the smoke southeast, and by July 15, skies turned hazy and air quality declined from southern Ontario in Canada to the Upper Midwest and Northeast in the U.S. July 16 and 17 saw air quality in many areas continue to plummet, including in Detroit, where it stayed in the hazardous range for several consecutive days. Toronto, Chicago, New York City, and Washington, D.C., saw air quality ranging from unhealthy to hazardous.

On July 19 and 20, smoke continued to affect air quality downwind, including in the Great Lakes region, according to the National Weather Service. Storms began clearing it away in parts of the East, where air quality improved to good or moderate. Meanwhile, fires in the Pacific Northwest began degrading air quality there.

The brown carbon shown in this animation represents organic carbon that comes specifically from wildfire smoke. Wildfires also emit black carbon, or soot, which contributes to their PM_2.5 output. Black carbon has long served as a tracer for smoke plumes, but human sources—such as vehicle exhaust and industrial combustion—produce it too, blending in with the black carbon from fires. The GEOS model has been able to make that distinction for brown carbon since February 2026, when an update enabled it to split organic carbon into its anthropogenic and biomass-burning components.

NASA Earth Observatory animation by Lauren Dauphin, using GEOS-FP data from the Global Modeling and Assimilation Office at NASA GSFC. Story by Kathryn Hansen.