Counties in Oregon by highest daily Air Quality Index (US EPA)

Linn County had the highest highest daily Air Quality Index (US EPA) of 25 counties in 2011, at 212. Coos County had the lowest, at 58. The median was 117. Source: the U.S. Environmental Protection Agency.

Highest212Linn County

Lowest58Coos County

Median11725 counties

Map of counties, 2011

Under 90
90 to 100
100 to 120
120 to 150
150 and over
No data

index, 2011. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2011

index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2011 index	Change on 2010
1	Linn County	212	+123
2	Deschutes County	176	+90
3	Lake County	165	+47
4	Union County	153	+47
5	Lane County	151	+24
6	Washington County	147	+34
7	Crook County	143	+41
8	Harney County	134	+16
9	Klamath County	130	-13
10	Multnomah County	127	+28
11	Grant County	122	-15
12	Jackson County	121	+28
13	Clackamas County	117	-55
14	Josephine County	106	+3
15	Umatilla County	104	+11
16	Jefferson County	99	-73
17	Marion County	96	-30
18	Baker County	95	+15
18	Douglas County	95	+27
20	Yamhill County	91	+19
21	Wallowa County	88	-74
22	Wasco County	87	-17
23	Benton County	86	+14
24	Columbia County	79	+8
25	Coos County	58	n/a

Other periods

About this ranking

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. 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. 1 counties with data in other periods have no value for 2011 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: highest daily AQI. 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: highest daily AQI (Counties in Oregon by highest daily Air Quality Index (US EPA), 2011) [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: highest daily AQI, Counties in Oregon by highest daily Air Quality Index (US EPA), 2011. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/oregon-counties?period=2011. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Counties in Oregon by highest daily Air Quality Index (US EPA), 2011. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/oregon-counties?period=2011.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Counties in Oregon by highest daily Air Quality Index (US EPA), 2011 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/highest-daily-air-quality-index/oregon-counties?period=2011 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_oregon_by_2011,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Counties in Oregon by highest daily Air Quality Index (US EPA), 2011}},
  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/highest-daily-air-quality-index/oregon-counties?period=2011. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. 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: highest daily AQI: Counties in Oregon by highest daily Air Quality Index (US EPA), 2011
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/highest-daily-air-quality-index/oregon-counties?period=2011
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/oregon-counties?period=2011.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -

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rank_places {"indicator":"aqi_max","level":"province","within":"Oregon","limit":10}
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Questions

Which county has the highest highest daily Air Quality Index (US EPA)?

Linn County, with 212 in 2011, according to the U.S. Environmental Protection Agency.

Which county has the lowest highest daily Air Quality Index (US EPA)?

Coos County, with 58 in 2011.

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: highest daily AQI. Retrieved 2026-10-12. 1 counties have no value for 2011 and are not ranked.