Data / Rankings / Median Air Quality Index (US EPA) / Counties in Oklahoma

Counties in Oklahoma by median Air Quality Index (US EPA), 2018

Tulsa County had the highest median Air Quality Index (US EPA) of 25 counties in 2018, at 56. Custer County had the lowest, at 16. The median was 42. Source: the U.S. Environmental Protection Agency.

Keep it in a collection in your library.
Highest56Tulsa County
Lowest16Custer County
Median4225 counties

Map of counties, 2018

Adair County: 42 indexBryan County: 38 indexCanadian County: 36 indexCarter County: 41 indexChoctaw County: 37 indexCleveland County: 52 indexComanche County: 44 indexCreek County: 36 indexCuster County: 16 indexDewey County: 47 indexJefferson County: 43 indexKay County: 51 indexLe Flore County: 34 indexLove County: 43 indexMcClain County: 38 indexMayes County: 37 indexMuskogee County: 19 indexNowata County: 48 indexOklahoma County: 52 indexOsage County: 36 indexOttawa County: 52 indexPittsburg County: 46 indexSequoyah County: 41 indexTulsa County: 56 indexWashington County: 53 index
  • Under 36
  • 36 to 40
  • 40 to 43
  • 43 to 51
  • 51 and over
  • No data
index, 2018. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2018

Tulsa County: 56 indexTulsa County56Washington County: 53 indexWashington County53Cleveland County: 52 indexCleveland County52Oklahoma County: 52 indexOklahoma County52Ottawa County: 52 indexOttawa County52Kay County: 51 indexKay County51Nowata County: 48 indexNowata County48Dewey County: 47 indexDewey County47Pittsburg County: 46 indexPittsburg County46Comanche County: 44 indexComanche County44Jefferson County: 43 indexJefferson County43Love County: 43 indexLove County43Adair County: 42 indexAdair County42Carter County: 41 indexCarter County41Sequoyah County: 41 indexSequoyah County41Bryan County: 38 indexBryan County38McClain County: 38 indexMcClain County38Choctaw County: 37 indexChoctaw County37Mayes County: 37 indexMayes County37Canadian County: 36 indexCanadian County36Creek County: 36 indexCreek County36Osage County: 36 indexOsage County36Le Flore County: 34 indexLe Flore County34Muskogee County: 19 indexMuskogee County19Custer County: 16 indexCuster County16Tulsa County: 56 indexTulsa County56Washington County: 53 indexWashington County53Cleveland County: 52 indexCleveland County52Oklahoma County: 52 indexOklahoma County52Ottawa County: 52 indexOttawa County52Kay County: 51 indexKay County51Nowata County: 48 indexNowata County48Dewey County: 47 indexDewey County47Pittsburg County: 46 indexPittsburg County46Comanche County: 44 indexComanche County44Jefferson County: 43 indexJefferson County43Love County: 43 indexLove County43Adair County: 42 indexAdair County42Carter County: 41 indexCarter County41Sequoyah County: 41 indexSequoyah County41Bryan County: 38 indexBryan County38McClain County: 38 indexMcClain County38Choctaw County: 37 indexChoctaw County37Mayes County: 37 indexMayes County37Canadian County: 36 indexCanadian County36Creek County: 36 indexCreek County36Osage County: 36 indexOsage County36Le Flore County: 34 indexLe Flore County34Muskogee County: 19 indexMuskogee County19Custer County: 16 indexCuster County16
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2018
index		Change on 2017
1Tulsa County56+2
2Washington County53+6
3Cleveland County52+5
3Oklahoma County52+1
3Ottawa County52+1
6Kay County51-2
7Nowata County48n/a
8Dewey County47+4
9Pittsburg County46+2
10Comanche County440
11Jefferson County43+2
11Love County43-1
13Adair County42-2
14Carter County41-2
14Sequoyah County41+3
16Bryan County38-1
16McClain County38-1
18Choctaw County37-1
18Mayes County37-1
20Canadian County36-2
20Creek County36-3
20Osage County36-3
23Le Flore County34n/a
24Muskogee County19-1
25Custer County16-1

Other periods

About this ranking

Median of the daily Air Quality Index (AQI) values of a US county over the days of the year with an AQI, from the EPA AirData annual summaries.

More on how it is measured
  • The daily county AQI is the highest AQI among the monitors and pollutants reported that day (ozone, PM2.5, PM10, carbon monoxide and nitrogen dioxide).
  • Lower is cleaner: 0 to 50 is good, 51 to 100 moderate and above 100 unhealthy for sensitive groups.

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 2018 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: median 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: median daily AQI (Counties in Oklahoma by median Air Quality Index (US EPA), 2018) [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: median daily AQI, Counties in Oklahoma by median Air Quality Index (US EPA), 2018. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/median-air-quality-index/oklahoma-counties. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Counties in Oklahoma by median Air Quality Index (US EPA), 2018. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/median-air-quality-index/oklahoma-counties.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Oklahoma by median Air Quality Index (US EPA), 2018 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/median-air-quality-index/oklahoma-counties (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_oklahoma_by_2018,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Oklahoma by median Air Quality Index (US EPA), 2018}},
  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/median-air-quality-index/oklahoma-counties. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median 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: median daily AQI: Counties in Oklahoma by median Air Quality Index (US EPA), 2018
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/median-air-quality-index/oklahoma-counties
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/oklahoma-counties.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
Embed this chart

Paste this code into a web page or a blog post. The chart shows the latest figures as they are published, with the source and a link back to this page.

Sites that read oEmbed links, such as WordPress, can show the chart when you paste the link to this page.

Use this data in your AI agent

Invokely serves this figure to AI assistants through MCP and to code through a REST API, with the source and citation attached. Ask your assistant:

Rank Counties in Oklahoma by median Air Quality Index (US EPA) using official data, and cite the source.
rank_places {"indicator":"aqi_median","level":"province","within":"Oklahoma","limit":10}
GET https://invokely.ai/api/v1/rank?indicator=aqi_median&level=province&within=Oklahoma&limit=10

Connect Claude, ChatGPT or Cursor in one step. The trial answers 25 calls a day without an account.

Questions

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

Tulsa County, with 56 in 2018, according to the U.S. Environmental Protection Agency.

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

Custer County, with 16 in 2018.

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: median daily AQI. Retrieved 2026-10-12. 20 counties have no value for 2018 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Oklahoma: more rankings