SmogRank / World / United States / Washington / May 2025

Most polluted cities in Washington, United States, May 2025

43 cities in Washington, United States ranked by their average PM2.5 over the 31 days. Worst: Anacortes at 8.0 µg/m³, #1,318 of 2,771 cities in the world. Cleanest: Mount Vernon at 1.6. A city needs measurements on 70% of the days to be ranked.

About 0 people in these 8 cities breathed unhealthy air on an average day of May 2025.

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.

← Yakima 0 0.750

Every city in Washington, United States ranked for May 2025 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.

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 2025 · All cities in United States, May 2025 · Washington now

Use this board

SmogRank, most polluted cities in Washington, United States, PM2.5, May 2025, smogrank.com/us/region/washington/history/2025-05 (accessed 6 Oct 2026).

Download top 10 (PNG)

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.