Wildfire activity in Canada increased in July 2026, a time of year when lightning ignition typically increases, according to a seasonal outlook published by several North American fire agencies. The fires caused plumes of smoke across the United States 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 an important component of fire particles_2.5 emissions, a type of air pollution that can aggravate cardiovascular and respiratory conditions. Here, the plume sweeps across the skies over North America from July 14 to 20, 2026.

The data for the animation comes from a version of the GEOS (Goddard Earth Observing System) model, which assimilates data from satellites, aircraft, and Earth observation systems. In addition to satellite observations of aerosols and fires, the model also incorporates meteorological data such as air temperature, humidity and winds to project the behavior of the plume.

By July 14, at the start of the animation, numerous fires had already broken out, including more than 180 in Ontario and several in northern Minnesota. Winds carried smoke southeastward, and by July 15, skies became hazy and air quality decreased from southern Ontario in Canada to the upper Midwest and Northeast in the U.S. On July 16 and 17, air quality in many areas continued to plummet, including in Detroit, where it remained in the hazardous range for several consecutive days. Toronto, Chicago, New York and Washington, DC all recorded air quality ranging from unhealthy to hazardous.

On July 19 and 20, smoke continued to impact air quality downwind, including in the Great Lakes region, according to the National Weather Service. Storms began to clear it in parts of the east, where air quality improved to good to moderate. Meanwhile, fires in the Pacific Northwest began to degrade air quality there.

The brown carbon shown in this animation represents organic carbon that comes specifically from wildfire smoke. Forest fires also emit black carbon or soot, which contributes to their PM._2.5 production. Black carbon has long served as a marker for smoke plumes, but human sources (such as vehicle exhaust and industrial combustion) also produce it, mixing with black carbon from fires. The GEOS model has been able to make that distinction for brown carbon since February 2026, when an update allowed it to split organic carbon into its anthropogenic and biomass-burning components.

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

• The Conversation (2026, July 16) Yes, breathing wildfire smoke can harm your health — here’s what you can do to protect yourself. Accessed July 21, 2026.
• NASA Office of Global Modeling and Assimilation (2026, February 19) Biomass Combustion and Anthropogenic Organic Carbon Sources Division in GOCART-2G. Accessed July 21, 2026.
• NASA Scientific Visualization Study (2026, July 20) Long-range transport of smoke from the 2026 Canadian wildfires to the United States (July 14-20, 2026). Accessed July 21, 2026.
• National Interagency Fire Centre, Natural Resources Canada and National Weather Service (2026, July 14) North American Seasonal Fire Assessment and Outlook. Accessed July 21, 2026.
• The New York Times (2026, July 19) When will wildfire smoke clear? Accessed July 21, 2026.
• US Environmental Protection Agency (2026, July 14-20) AirNow: Interactive air quality map. Accessed July 21, 2026.