Unprecedented Wildfires in the Pacific Northwest Engulf the Region in Smoke

Wildfires can have a profound impact on society through their effects on air quality, destruction of homes, and resulting changes to the land surface. From an air quality perspective, wildfires emit toxic gases and fine particulate matter that are harmful to human health. Locally, wildfires can also cause water contamination, habitat loss, and property destruction. It is therefore important to understand the extent of a wildfire and where the smoke can be transported to provide sufficient warning for preparation and evacuation, including air quality alerts than can be hundreds of miles away.

Wildfires have been prevalent in Oregon, Washington, and British Columbia since mid-July due to abnormally hot and dry conditions, at a time when the eastern United States was impacted by smoke from Ontario. The entire state of Oregon and nearly all of Washington were under moderate to extreme drought conditions, which primed the land surface for dangerous fire weather conditions. The fire weather index, calculated using data from NASA’s Goddard Earth Observing System (GEOS), considers conditions that are favorable for a fire igniting and spreading, such as local wind speed and precipitation over time. Using the fire weather index for August 1, 2026 as an example to coincide with rapid increase in fires near Spokane, Washington, there was a high likelihood of fire across much of the western United States; however, fires were exceptionally likely in eastern Washington.

Using wavelengths outside of the visible spectrum, imagery provided by the Sentinel satellite shows burn scars and the perimeter of the fires in Oregon and Washington State. This demonstrates the extent of the wildfires in eastern Washington State and their proximity to farmland and residential areas. A closer view of the fires surrounding Spokane, Washington, reveals that wildfires do not have boundaries. They can jump across rivers and highways, resulting in destroyed homes and upended lives.

While the imagery provided by satellites details the local impacts of the wildfires, Earth system models are a valuable tool for tracking the long-range transport of wildfire smoke. This visualization shows the aerosol optical depth (AOD) associated with brown carbon in a replay using NASA’s Goddard Earth Observing System Convection Allowing Model (GEOS-CAM). Brown carbon AOD serves as a proxy for biomass burning aerosol such that the dark brown shading represents dense plumes of smoke. Although not always the case, high values of AOD associated with brown carbon could indicate that air quality conditions are degraded. The meteorology within GEOS-CAM is observationally constrained using satellite and conventional observations, allowing for a realistic representation of how the smoke is transported.

In addition to the poor air quality close to the wildfires themselves, smoke from these wildfires was transported eastward, degrading the air quality across southern Canada, Idaho, Montana, and North Dakota, before eventually reaching the East Coast of the United States in late July. The clusters of wildfires in the Pacific Northwest persisted for weeks, with fluctuations in their intensity. Shifts in the local wind direction and large-scale steering currents, in addition to a low-pressure system that made its way across the United States, resulted in smoke from these wildfires reaching most of the continental United States.