Seattle wildfire smoke forecast
The map above shows NOAA HRRR-Smoke near-surface PM2.5 for the next 48 hours, updated hourly, with active fires from NIFC and live AQI from EPA AirNow monitors. It opens over Seattle.
Seattle sits near sea level on the Puget Sound lowland, in a trough between the Olympics to the west and the Cascades to the east. Marine air normally floods that trough and keeps the city's baseline air clean, which is exactly why smoke episodes here feel so abrupt: the lowland has no local pollution problem to hide behind, and the same shallow marine layer that usually ventilates the city will cap smoke in place once the flow reverses.
Where the smoke comes from
Almost none of Seattle's smoke is made in Seattle. The three suppliers are the British Columbia interior, the Okanogan and Methow country east of the Cascades, and the Cascade crest itself. All three need an easterly or northerly component to the wind to reach Puget Sound, which is why a large fire can burn for a week with no effect on the city and then deliver a bad-air day the moment the pattern flips. August and September are the months that matter.
How long it lasts
One mechanism ends it: onshore flow. When the marine push returns through the Strait of Juan de Fuca and over the Chehalis Gap, clean Pacific air scours the lowland, often within a single afternoon. Until that happens, no amount of local wind helps, because the surrounding terrain keeps recirculating the same air. Watch the forecast for a westerly shift rather than for the fire to be contained.
Past smoke events
August 2018 held the region in smoke for roughly two weeks. The Labor Day windstorm of September 2020 pushed Seattle into the worst measured air quality of any major city in the world for several days, and the 2022 Bolt Creek Fire put smoke into the city through most of October, unusually late in the season.
Running, riding, and trailheads
Discovery Park, the Burke-Gilman, and the Snoqualmie and Mountain Loop trailheads are the usual casualties. Elevation is not a reliable escape here the way it is in the Rockies, because the smoke layer over Puget Sound is often deep rather than shallow. Checking the hour-by-hour forecast before driving east to a trailhead is worth more than checking the current reading in town.
Reading the map
Use the layer toggle to compare NOAA HRRR-Smoke with the ECCC FireWork model. When the two disagree, treat the higher reading as the cautious call.
Near-surface is the product that maps to what you breathe and to AQI, not the high-altitude column that only tints the sunset. A sky that looks bad and a monitor that reads fine are usually both correct, and they are describing different layers of air.