Air quality across the Pacific Northwest is showing a split pattern this week: communities west of the Cascades are benefiting from rain and onshore marine flow, while eastern Washington and Idaho continue to experience elevated smoke levels tied to ongoing regional fire activity and regional smoke transport.

Eastern Washington: Elevated Smoke in the Tri-Cities and Columbia Basin

Kennewick recorded an Air Quality Index (AQI) of 108 — in the Unhealthy for Sensitive Groups range — on September 25, driven by a combination of regional wildfire smoke drift and particulate matter from the arid Columbia Basin agricultural region. The Second Street Fire burning near Benton City is adding fresh smoke to already-elevated conditions in the Tri-Cities corridor.

People in eastern Washington's Unhealthy for Sensitive Groups range should take the following precautions:

  • Limit prolonged outdoor exertion, especially for children, older adults, and those with heart or lung conditions
  • Keep windows and doors closed when possible
  • Run air purifiers with HEPA filters indoors
  • Wear an N95 or KN95 mask if outdoor activity is unavoidable

Idaho: Unhealthy Levels in Southern and Panhandle Communities

Idaho saw some of the worst air quality in the Pacific Northwest this week. Pocatello recorded an AQI of 154 — reaching the Unhealthy category — on September 22, attributed to wildfire smoke from active regional fires trapped by valley temperature inversions typical of the area. At AQI levels above 150, even healthy adults are advised to limit prolonged outdoor exertion.

Pinehurst, in the Silver Valley area of northern Idaho, recorded an AQI of 105 as of Saturday morning — Unhealthy for Sensitive Groups — with smoke from the Upper Smith Fire on the Idaho Panhandle National Forest and regional transport contributing to elevated readings. The Silver Valley's steep terrain frequently traps smoke during inversion conditions, worsening local air quality.

Western Communities Getting Relief

The situation is considerably better west of the Cascade crest. Portland's AQI dropped to 26 — the Good category — earlier this week, and Seattle readings have remained mostly Moderate or better. The National Interagency Fire Center's September 25 weather report notes that widespread rainfall is expected near and west of the Cascades in Oregon and Washington, which should continue to improve air quality in those areas over the coming days.

Wetting rain is also expected in northern Idaho and western Montana, which may provide some relief to communities in those areas that have been struggling with smoke for extended periods.

Monitoring Resources

Residents across the Pacific Northwest can track real-time air quality conditions using these resources:

  • AirNow.gov — official EPA air quality data and forecasts
  • PurpleAir — community-based sensor network with hyperlocal readings
  • Washington DOE Air Quality — waqa.ecology.wa.gov
  • Oregon DEQ Air Quality — oregonairqualityindex.org
  • Idaho DEQ Air Quality — deq.idaho.gov/air

Health agencies recommend that sensitive groups — including children, older adults, pregnant women, and anyone with respiratory or cardiovascular conditions — check air quality before outdoor activities any time wildfire smoke may be present in the region.