Counties with the Worst Air Quality in Washington
The top 25 of 31 Washington counties on GIS Map, ranked by median Air Quality Index, counting only counties that host an EPA air monitor.
| # | County | Median AQI |
|---|---|---|
| 1 | Pierce County | 44 |
| 2 | Asotin County | 42 |
| 3 | King County | 41 |
| 4 | Okanogan County | 38 |
| 5 | Snohomish County | 38 |
| 6 | Spokane County | 38 |
| 7 | Yakima County | 37 |
| 8 | Clallam County | 36 |
| 9 | Columbia County | 36 |
| 10 | Benton County | 34 |
| 11 | Stevens County | 34 |
| 12 | Whatcom County | 33 |
| 13 | Clark County | 31 |
| 14 | Chelan County | 28 |
| 15 | Grant County | 26 |
| 16 | Skagit County | 26 |
| 17 | Thurston County | 26 |
| 18 | Walla Walla County | 24 |
| 19 | Kittitas County | 23 |
| 20 | Cowlitz County | 22 |
| 21 | Lewis County | 22 |
| 22 | Jefferson County | 21 |
| 23 | Mason County | 21 |
| 24 | Franklin County | 20 |
| 25 | Grays Harbor County | 20 |
Source: EPA Air Quality Index annual summary (2024). All counties with data are ranked. Estimates carry margins of error.
Citing this page: GIS Map, “Counties with the Worst Air Quality in Washington”, https://gismap.land/rankings/washington/worst-air-quality-counties. Figures from EPA Air Quality Index annual summary (2024).
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