Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Washington

Counties in Washington by share of days with good air quality (US EPA AQI)

Jefferson County had the highest share of days with good air quality (US EPA AQI) of 31 counties in 2022, at 93.7%. Okanogan County had the lowest, at 47.9%. The median was 80%. Source: EPA.

Keep it in a collection in your library.
Highest93.7Jefferson County
Lowest47.9Okanogan County
Median8031 counties

Map of counties, 2022

Adams County: 89.6 %Asotin County: 54.5 %Benton County: 76.2 %Chelan County: 67.4 %Clallam County: 74.5 %Clark County: 73.2 %Columbia County: 86 %Cowlitz County: 87.1 %Franklin County: 82 %Garfield County: 87.4 %Grant County: 76.4 %Grays Harbor County: 93.2 %Jefferson County: 93.7 %King County: 59.2 %Kitsap County: 85.2 %Kittitas County: 71.2 %Klickitat County: 88 %Lewis County: 78.1 %Mason County: 82.7 %Okanogan County: 47.9 %Pend Oreille County: 88.5 %Pierce County: 65.5 %Skagit County: 85.8 %Snohomish County: 58 %Spokane County: 69.6 %Stevens County: 57 %Thurston County: 88.8 %Walla Walla County: 80 %Whatcom County: 85.7 %Whitman County: 83.8 %Yakima County: 48.8 %
  • Under 59
  • 59 to 73
  • 73 to 80
  • 80 to 86
  • 86 to 88
  • 88 and over
  • No data
%, 2022. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2022

Jefferson County: 93.7 %Jefferson County93.7Grays Harbor County: 93.2 %Grays Harbor County93.2Adams County: 89.6 %Adams County89.6Thurston County: 88.8 %Thurston County88.8Pend Oreille County: 88.5 %Pend Oreille County88.5Klickitat County: 88 %Klickitat County88Garfield County: 87.4 %Garfield County87.4Cowlitz County: 87.1 %Cowlitz County87.1Columbia County: 86 %Columbia County86Skagit County: 85.8 %Skagit County85.8Whatcom County: 85.7 %Whatcom County85.7Kitsap County: 85.2 %Kitsap County85.2Whitman County: 83.8 %Whitman County83.8Mason County: 82.7 %Mason County82.7Franklin County: 82 %Franklin County82Walla Walla County: 80 %Walla Walla County80Lewis County: 78.1 %Lewis County78.1Grant County: 76.4 %Grant County76.4Benton County: 76.2 %Benton County76.2Clallam County: 74.5 %Clallam County74.5Clark County: 73.2 %Clark County73.2Kittitas County: 71.2 %Kittitas County71.2Spokane County: 69.6 %Spokane County69.6Chelan County: 67.4 %Chelan County67.4Pierce County: 65.5 %Pierce County65.5King County: 59.2 %King County59.2Snohomish County: 58 %Snohomish County58Stevens County: 57 %Stevens County57Asotin County: 54.5 %Asotin County54.5Yakima County: 48.8 %Yakima County48.8Okanogan County: 47.9 %Okanogan County47.9Jefferson County: 93.7 %Jefferson County93.7Grays Harbor County: 93.2 %Grays Harbor County93.2Adams County: 89.6 %Adams County89.6Thurston County: 88.8 %Thurston County88.8Pend Oreille County: 88.5 %Pend Oreille County88.5Klickitat County: 88 %Klickitat County88Garfield County: 87.4 %Garfield County87.4Cowlitz County: 87.1 %Cowlitz County87.1Columbia County: 86 %Columbia County86Skagit County: 85.8 %Skagit County85.8Whatcom County: 85.7 %Whatcom County85.7Kitsap County: 85.2 %Kitsap County85.2Whitman County: 83.8 %Whitman County83.8Mason County: 82.7 %Mason County82.7Franklin County: 82 %Franklin County82Walla Walla County: 80 %Walla Walla County80Lewis County: 78.1 %Lewis County78.1Grant County: 76.4 %Grant County76.4Benton County: 76.2 %Benton County76.2Clallam County: 74.5 %Clallam County74.5Clark County: 73.2 %Clark County73.2Kittitas County: 71.2 %Kittitas County71.2Spokane County: 69.6 %Spokane County69.6Chelan County: 67.4 %Chelan County67.4Pierce County: 65.5 %Pierce County65.5King County: 59.2 %King County59.2Snohomish County: 58 %Snohomish County58Stevens County: 57 %Stevens County57Asotin County: 54.5 %Asotin County54.5Yakima County: 48.8 %Yakima County48.8Okanogan County: 47.9 %Okanogan County47.9
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2022 (%)Change on 2021
1Jefferson County93.7-4.6 pts
2Grays Harbor County93.2-1.9 pts
3Adams County89.6-1.9 pts
4Thurston County88.8-5.1 pts
5Pend Oreille County88.5+17.7 pts
6Klickitat County88+1.4 pts
7Garfield County87.4+2.4 pts
8Cowlitz County87.1-10.2 pts
9Columbia County86+2.7 pts
10Skagit County85.8-8.5 pts
11Whatcom County85.7-11.6 pts
12Kitsap County85.2-10.1 pts
13Whitman County83.8-1.1 pts
14Mason County82.7-11.2 pts
15Franklin County82-10.8 pts
16Walla Walla County80-4.7 pts
17Lewis County78.1-15.6 pts
18Grant County76.4-8.5 pts
19Benton County76.2-1.3 pts
20Clallam County74.5-7.1 pts
21Clark County73.2-11.2 pts
22Kittitas County71.2-11.8 pts
23Spokane County69.6+3.3 pts
24Chelan County67.4-9 pts
25Pierce County65.5-8.2 pts
26King County59.2-8.7 pts
27Snohomish County58-9.9 pts
28Stevens County57+1.4 pts
29Asotin County54.5+2 pts
30Yakima County48.8+0.9 pts
31Okanogan County47.9+7.9 pts

Other periods

About this ranking

Days with a daily Air Quality Index of 0 to 50 (good) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; both counts are stored with each value.

United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. 3 counties with data in other periods have no value for 2022 and are left out rather than filled from another source. Equal values share a rank.

How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts (Counties in Washington by share of days with good air quality (US EPA AQI), 2022) [Data set]. Retrieved October 12, 2026, from https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual

MLA 9

EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Washington by share of days with good air quality (US EPA AQI), 2022. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/good-air-quality-days-share/washington-counties?period=2022. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Counties in Washington by share of days with good air quality (US EPA AQI), 2022. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/good-air-quality-days-share/washington-counties?period=2022.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Washington by share of days with good air quality (US EPA AQI), 2022 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/washington-counties?period=2022 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_washington_by_2022,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Washington by share of days with good air quality (US EPA AQI), 2022}},
  year = {2026},
  howpublished = {Data set},
  url = {https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/washington-counties?period=2022. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download\_files.html\#Annual. Retrieved 2026-10-12.},
}
RIS
TY  - DATA
AU  - U.S. Environmental Protection Agency
TI  - EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Washington by share of days with good air quality (US EPA AQI), 2022
PY  - 2026
DA  - 2026/07/13
PB  - U.S. Environmental Protection Agency
DB  - Invokely
UR  - https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual
L2  - https://invokely.ai/rankings/good-air-quality-days-share/washington-counties?period=2022
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/washington-counties?period=2022.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Questions

Which county has the highest share of days with good air quality (US EPA AQI)?

Jefferson County, with 93.7% in 2022, according to EPA.

Which county has the lowest share of days with good air quality (US EPA AQI)?

Okanogan County, with 47.9% in 2022.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 3 counties have no value for 2022 and are not ranked.

Share of days with good air quality (US EPA AQI): other rankings

Counties in Washington: more rankings