Air Quality Rankings for Washington 2026

Washington has 30 cities with EPA air quality data. Adams, Washington has the cleanest air with a 5-year average AQI of 18. Yakima, Washington has the highest AQI at 49.

#	City	5yr Avg AQI	Current AQI	Worst Pollutant	Trend	Grade
1	Adams, Washington	18	21	PM2.5	Improving	B
2	Garfield, Washington	20	17	PM2.5	Improving	A
3	Klickitat, Washington	22	20	PM2.5	Stable	B
4	Cowlitz, Washington	22	22	PM2.5	Improving	B
5	Franklin, Washington	22	26	PM2.5	Stable	B
6	Jefferson, Washington	22	21	PM2.5	Improving	B
7	Whitman, Washington	23	26	PM2.5	Stable	B
8	Mason, Washington	24	24	PM2.5	Improving	B
9	Kitsap, Washington	25	22	PM2.5	Worsening	B
10	Grays Harbor, Washington	25	23	PM2.5	Improving	B
11	Lewis, Washington	25	25	PM2.5	Improving	B
12	Walla Walla, Washington	25	28	PM2.5	Worsening	B
13	Grant, Washington	26	32	PM2.5	Stable	B
14	Thurston, Washington	27	28	PM2.5	Improving	B
15	Kittitas, Washington	28	29	PM2.5	Worsening	B
16	Skagit, Washington	28	30	PM2.5	Improving	B
17	Whatcom, Washington	29	31	PM2.5	Improving	B
18	Chelan, Washington	32	34	PM2.5	Stable	C
19	Columbia, Washington	32	39	PM2.5	Worsening	C
20	Clark, Washington	34	35	PM2.5	Stable	B
21	Clallam, Washington	37	37	PM2.5	Improving	B
22	Benton, Washington	38	41	PM2.5	Worsening	C
23	Snohomish, Washington	38	38	PM2.5	Stable	C
24	Spokane, Washington	41	42	PM2.5	Improving	B
25	Stevens, Washington	42	46	PM2.5	Worsening	C
26	Pierce, Washington	43	42	Ozone	Stable	C
27	Asotin, Washington	43	49	PM2.5	Worsening	D
28	King, Washington	45	46	PM2.5	Improving	C
29	Okanogan, Washington	49	49	PM2.5	Worsening	C
30	Yakima, Washington	49	46	PM2.5	Worsening	C

Air quality data for Washington is sourced from the EPA Air Quality System (AQS), which monitors outdoor air quality at thousands of stations nationwide.
— EPA Air Quality System

Frequently Asked Questions

Adams, Washington has the best air quality in Washington with a 5-year average AQI of 18 and a grade of B.

Washington has 30 cities with EPA air quality monitoring data in our database, covering multiple years of AQI measurements.

The Air Quality Index (AQI) measures five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Lower AQI values indicate cleaner air — 0-50 is "Good," while 150+ is "Unhealthy."

Sources: EPA Air Quality System (AQS)

Cities ranked by 5-year average AQI (lower is better). Grades factor in average AQI, trend direction, unhealthy days, and dominant pollutant.

Cleanest Cities Nationwide →All Air Quality in Washington →