Wildfire activity in Canada intensified in July 2026, a period when lightning‑induced ignitions are common, as noted in a seasonal forecast from multiple North American fire agencies. The resulting blazes released extensive smoke plumes that traveled across both the United States and Canada, degrading air quality in the affected regions.
The animation illustrates brown carbon—organic aerosols produced by wildfires that impart a yellow, orange, or brown hue to smoke plumes. As a significant fraction of PM2.5, brown carbon can worsen cardiovascular and respiratory health. The depicted plume traverses North American skies between July 14 and July 20, 2026.
Data for this visualization are derived from the GEOS (Goddard Earth Observing System) model, which integrates satellite, aircraft, and ground‑based observations. Beyond aerosol and fire detections, the model also incorporates meteorological variables—including temperature, humidity, and wind—to simulate the plume’s evolution.
The animation begins on July 14, when dozens of fires were already active, including over 180 in Ontario and several in northern Minnesota. Southeast winds transported the smoke across the border, leading to hazy conditions and reduced air quality from southern Ontario through the Upper Midwest and Northeast U.S. On July 16 and 17, air quality continued to deteriorate, reaching hazardous levels in Detroit for several days. Cities such as Toronto, Chicago, New York City, and Washington, D.C., recorded air quality ranging from unhealthy to hazardous.
By July 19 and 20, the smoke persisted downwind, notably across the Great Lakes region, as reported by the National Weather Service. Storms in the eastern United States started to disperse the plume, restoring air quality to good or moderate levels in some areas. Simultaneously, wildfires in the Pacific Northwest began to impair local air quality.
In this animation, brown carbon denotes organic carbon emitted exclusively by wildfire smoke. Wildfires also release black carbon (soot), a component of PM2.5 emissions. Although black carbon is traditionally used as a smoke tracer, anthropogenic sources—such as vehicle exhaust and industrial combustion—also generate it, mixing with fire‑derived black carbon. Since February 2026, an update to the GEOS model has enabled it to differentiate brown carbon by separating organic carbon into anthropogenic and biomass‑burning contributions.
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.