SmogRank / World / United States / Washington / May 2026

Most polluted cities in Washington, United States, May 2026

48 cities in Washington, United States ranked by their average PM2.5 over the 31 days. Worst: Redmond at 9.3 µg/m³, #920 of 2,852 cities in the world. Cleanest: Union Hill-Novelty Hill at 2.1. A city needs measurements on 70% of the days to be ranked.

About 6.49K people in these 12 cities breathed unhealthy air on an average day of May 2026.

Ranked by people: each city's population times its share of unhealthy days, those with a daily mean over 35.4 µg/m³ (US AQI 101+). That is how many people living there breathed unhealthy air on an average day. Only cities measured at 2 or more places at least 3 km apart are ranked: one monitor shouldn't speak for a whole city. Population is the city itself, not its wider metro area.

← Redmond 6.49K 6K0
Every city in Washington, United States ranked for May 2026 with monitors in two or more places, one column each, ranked by people breathing unhealthy air: height is people on an average day, colour its average. Point at it to read a city; tap to open it.
  1. 1Redmondlow-cost sensors
    6.49K
  2. 2Seattle
    0
  3. 3Tri-Cities
    0
  4. 4Wenatchee
    0
  5. 5Toppenish
    0
  6. 6Spokane
    0
  7. 6Spokane Valley
    0
  8. 8Mead
    0
  9. 9Yakima
    0
  10. 10Kirklandlow-cost sensors
    0
  11. 11Bothelllow-cost sensors
    0
  12. 11Union Hill-Novelty Hilllow-cost sensors
    0

Low-cost sensors: consumer units, counted only in cities with no government-grade monitor; they read close to reference monitors on the whole, but 15 to 25% high in humid air. How we use them.

Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales

All cities in the world, May 2026 · All cities in United States, May 2026 · Washington now

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SmogRank, most polluted cities in Washington, United States, PM2.5, May 2026, smogrank.com/us/region/washington/history/2026-05 (accessed 6 Oct 2026).

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.