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

Custer County had the highest share of days with good air quality (US EPA AQI) of 25 counties in 2004, at 100%. Tulsa County had the lowest, at 38.5%. The median was 72.3%. Source: EPA.

Highest100Custer County

Lowest38.5Tulsa County

Median72.325 counties

Map of counties, 2004

Under 55
55 to 70
70 to 76
76 to 82
82 and over
No data

%, 2004. 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, 2004

%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2004 (%)	Change on 2003
1	Custer County	100	0 pts
2	McClain County	90.9	+13.4 pts
3	Cleveland County	82.8	+3.6 pts
4	Canadian County	82.5	+10.7 pts
5	Dewey County	82.2	+9.9 pts
6	Creek County	81.6	+12.7 pts
7	Johnston County	79.8	+7.8 pts
8	Ellis County	77.8	+13.6 pts
9	Muskogee County	77.4	+2.1 pts
10	Cherokee County	77.3	+7.4 pts
11	Ottawa County	75.3	+11.8 pts
12	Adair County	73.3	+0.8 pts
13	Cotton County	72.3	+8.9 pts
14	Pittsburg County	72	+5.9 pts
15	Comanche County	70.4	-0.8 pts
16	Mayes County	69.5	+36.2 pts
17	Carter County	65.1	+15.6 pts
18	Kay County	65	+10.8 pts
19	Caddo County	56.9	+3.2 pts
20	Garfield County	55.7	+8.1 pts
21	Sequoyah County	51.4	n/a
22	Lincoln County	50.8	+5.2 pts
23	Oklahoma County	47	+11.4 pts
24	Seminole County	43.9	+2.5 pts
25	Tulsa County	38.5	+8.9 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. 20 counties with data in other periods have no value for 2004 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 Oklahoma by share of days with good air quality (US EPA AQI), 2004) [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 Oklahoma by share of days with good air quality (US EPA AQI), 2004. 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/oklahoma-counties?period=2004. 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 Oklahoma by share of days with good air quality (US EPA AQI), 2004. 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/oklahoma-counties?period=2004.

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 Oklahoma by share of days with good air quality (US EPA AQI), 2004 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/oklahoma-counties?period=2004 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_oklahoma_by_2004,
  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 Oklahoma by share of days with good air quality (US EPA AQI), 2004}},
  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/oklahoma-counties?period=2004. 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 Oklahoma by share of days with good air quality (US EPA AQI), 2004
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/oklahoma-counties?period=2004
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/oklahoma-counties?period=2004.
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)?

Custer County, with 100% in 2004, according to EPA.

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

Tulsa County, with 38.5% in 2004.

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. 20 counties have no value for 2004 and are not ranked.