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)

Benton County had the highest share of days with good air quality (US EPA AQI) of 23 counties in 2021, at 94.5%. Klamath County had the lowest, at 44.4%. The median was 76.7%. Source: EPA.

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Highest94.5Benton County
Lowest44.4Klamath County
Median76.723 counties

Map of counties, 2021

Baker County: 74.5 %Benton County: 94.5 %Clackamas County: 90.4 %Columbia County: 92.5 %Crook County: 77 %Deschutes County: 81.6 %Douglas County: 83.3 %Grant County: 48.8 %Harney County: 52.3 %Jackson County: 55.9 %Jefferson County: 77.3 %Josephine County: 65.8 %Klamath County: 44.4 %Lake County: 65.8 %Lane County: 58.6 %Linn County: 73.4 %Marion County: 77.1 %Multnomah County: 80.5 %Umatilla County: 72.6 %Union County: 84.4 %Wallowa County: 76.7 %Wasco County: 90 %Washington County: 75.6 %
  • Under 61
  • 61 to 74
  • 74 to 77
  • 77 to 84
  • 84 and over
  • No data
%, 2021. 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, 2021

Benton County: 94.5 %Benton County94.5Columbia County: 92.5 %Columbia County92.5Clackamas County: 90.4 %Clackamas County90.4Wasco County: 90 %Wasco County90Union County: 84.4 %Union County84.4Douglas County: 83.3 %Douglas County83.3Deschutes County: 81.6 %Deschutes County81.6Multnomah County: 80.5 %Multnomah County80.5Jefferson County: 77.3 %Jefferson County77.3Marion County: 77.1 %Marion County77.1Crook County: 77 %Crook County77Wallowa County: 76.7 %Wallowa County76.7Washington County: 75.6 %Washington County75.6Baker County: 74.5 %Baker County74.5Linn County: 73.4 %Linn County73.4Umatilla County: 72.6 %Umatilla County72.6Josephine County: 65.8 %Josephine County65.8Lake County: 65.8 %Lake County65.8Lane County: 58.6 %Lane County58.6Jackson County: 55.9 %Jackson County55.9Harney County: 52.3 %Harney County52.3Grant County: 48.8 %Grant County48.8Klamath County: 44.4 %Klamath County44.4Benton County: 94.5 %Benton County94.5Columbia County: 92.5 %Columbia County92.5Clackamas County: 90.4 %Clackamas County90.4Wasco County: 90 %Wasco County90Union County: 84.4 %Union County84.4Douglas County: 83.3 %Douglas County83.3Deschutes County: 81.6 %Deschutes County81.6Multnomah County: 80.5 %Multnomah County80.5Jefferson County: 77.3 %Jefferson County77.3Marion County: 77.1 %Marion County77.1Crook County: 77 %Crook County77Wallowa County: 76.7 %Wallowa County76.7Washington County: 75.6 %Washington County75.6Baker County: 74.5 %Baker County74.5Linn County: 73.4 %Linn County73.4Umatilla County: 72.6 %Umatilla County72.6Josephine County: 65.8 %Josephine County65.8Lake County: 65.8 %Lake County65.8Lane County: 58.6 %Lane County58.6Jackson County: 55.9 %Jackson County55.9Harney County: 52.3 %Harney County52.3Grant County: 48.8 %Grant County48.8Klamath County: 44.4 %Klamath County44.4
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2021 (%)Change on 2020
1Benton County94.5+9 pts
2Columbia County92.5+1 pts
3Clackamas County90.4+2.9 pts
4Wasco County90+3.5 pts
5Union County84.4+2.4 pts
6Douglas County83.3+7.3 pts
7Deschutes County81.6+0.2 pts
8Multnomah County80.5+5.4 pts
9Jefferson County77.3+5.8 pts
10Marion County77.1+0.9 pts
11Crook County77+5.5 pts
12Wallowa County76.7-2 pts
13Washington County75.6+3.2 pts
14Baker County74.5-2.5 pts
15Linn County73.4+6.5 pts
16Umatilla County72.6-2 pts
17Josephine County65.8+3.5 pts
17Lake County65.8-7.4 pts
19Lane County58.6+3.1 pts
20Jackson County55.9-3.7 pts
21Harney County52.3-5.4 pts
22Grant County48.8-5 pts
23Klamath County44.4-2.6 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 2021 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), 2021) [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), 2021. 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=2021. 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), 2021. 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=2021.

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), 2021 [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=2021 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_oregon_by_2021,
  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), 2021}},
  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=2021. 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), 2021
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=2021
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/oregon-counties?period=2021.
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)?

Benton County, with 94.5% in 2021, according to EPA.

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

Klamath County, with 44.4% in 2021.

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 2021 and are not ranked.

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

Counties in Oregon: more rankings