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

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

Columbia County had the highest share of days with good air quality (US EPA AQI) of 23 counties in 2020, at 91.5%. Klamath County had the lowest, at 47%. The median was 74.6%. Source: EPA.

Keep it in a collection in your library.
Highest91.5Columbia County
Lowest47Klamath County
Median74.623 counties

Map of counties, 2020

Baker County: 77 %Benton County: 85.5 %Clackamas County: 87.5 %Columbia County: 91.5 %Crook County: 71.5 %Deschutes County: 81.4 %Douglas County: 76 %Grant County: 53.8 %Harney County: 57.7 %Jackson County: 59.6 %Jefferson County: 71.5 %Josephine County: 62.3 %Klamath County: 47 %Lake County: 73.2 %Lane County: 55.5 %Linn County: 66.9 %Marion County: 76.2 %Multnomah County: 75.1 %Umatilla County: 74.6 %Union County: 82 %Wallowa County: 78.7 %Wasco County: 86.5 %Washington County: 72.4 %
  • Under 61
  • 61 to 72
  • 72 to 76
  • 76 to 82
  • 82 and over
  • No data
%, 2020. 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, 2020

Columbia County: 91.5 %Columbia County91.5Clackamas County: 87.5 %Clackamas County87.5Wasco County: 86.5 %Wasco County86.5Benton County: 85.5 %Benton County85.5Union County: 82 %Union County82Deschutes County: 81.4 %Deschutes County81.4Wallowa County: 78.7 %Wallowa County78.7Baker County: 77 %Baker County77Marion County: 76.2 %Marion County76.2Douglas County: 76 %Douglas County76Multnomah County: 75.1 %Multnomah County75.1Umatilla County: 74.6 %Umatilla County74.6Lake County: 73.2 %Lake County73.2Washington County: 72.4 %Washington County72.4Crook County: 71.5 %Crook County71.5Jefferson County: 71.5 %Jefferson County71.5Linn County: 66.9 %Linn County66.9Josephine County: 62.3 %Josephine County62.3Jackson County: 59.6 %Jackson County59.6Harney County: 57.7 %Harney County57.7Lane County: 55.5 %Lane County55.5Grant County: 53.8 %Grant County53.8Klamath County: 47 %Klamath County47Columbia County: 91.5 %Columbia County91.5Clackamas County: 87.5 %Clackamas County87.5Wasco County: 86.5 %Wasco County86.5Benton County: 85.5 %Benton County85.5Union County: 82 %Union County82Deschutes County: 81.4 %Deschutes County81.4Wallowa County: 78.7 %Wallowa County78.7Baker County: 77 %Baker County77Marion County: 76.2 %Marion County76.2Douglas County: 76 %Douglas County76Multnomah County: 75.1 %Multnomah County75.1Umatilla County: 74.6 %Umatilla County74.6Lake County: 73.2 %Lake County73.2Washington County: 72.4 %Washington County72.4Crook County: 71.5 %Crook County71.5Jefferson County: 71.5 %Jefferson County71.5Linn County: 66.9 %Linn County66.9Josephine County: 62.3 %Josephine County62.3Jackson County: 59.6 %Jackson County59.6Harney County: 57.7 %Harney County57.7Lane County: 55.5 %Lane County55.5Grant County: 53.8 %Grant County53.8Klamath County: 47 %Klamath County47
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2020 (%)Change on 2019
1Columbia County91.5-2.7 pts
2Clackamas County87.5-7.6 pts
3Wasco County86.5+11.6 pts
4Benton County85.5+2.8 pts
5Union County82-3.8 pts
6Deschutes County81.4-3.3 pts
7Wallowa County78.7-0.9 pts
8Baker County77-4.4 pts
9Marion County76.2+2.6 pts
10Douglas County76+2.2 pts
11Multnomah County75.1-2.4 pts
12Umatilla County74.6+1.4 pts
13Lake County73.2-6.1 pts
14Washington County72.4-1 pts
15Crook County71.5-1.4 pts
15Jefferson County71.50 pts
17Linn County66.9+3.1 pts
18Josephine County62.3-6.5 pts
19Jackson County59.6-8.6 pts
20Harney County57.7+1.7 pts
21Lane County55.5-3.7 pts
22Grant County53.8-4.9 pts
23Klamath County47-16 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 2020 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 Oregon by share of days with good air quality (US EPA AQI), 2020) [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 Oregon by share of days with good air quality (US EPA AQI), 2020. 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/oregon-counties?period=2020. 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 Oregon by share of days with good air quality (US EPA AQI), 2020. 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/oregon-counties?period=2020.

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 Oregon by share of days with good air quality (US EPA AQI), 2020 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/oregon-counties?period=2020 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_oregon_by_2020,
  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 Oregon by share of days with good air quality (US EPA AQI), 2020}},
  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/oregon-counties?period=2020. 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 Oregon by share of days with good air quality (US EPA AQI), 2020
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/oregon-counties?period=2020
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/oregon-counties?period=2020.
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)?

Columbia County, with 91.5% in 2020, according to EPA.

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

Klamath County, with 47% in 2020.

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 2020 and are not ranked.

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

Counties in Oregon: more rankings