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

Johnson County had the highest share of days with good air quality (US EPA AQI) of 18 counties in 2013, at 98.1%. Campbell County had the lowest, at 56.2%. The median was 82.8%. Source: EPA.

Highest98.1Johnson County

Lowest56.2Campbell County

Median82.818 counties

Map of counties, 2013

Under 72
72 to 81
81 to 86
86 to 94
94 and over
No data

%, 2013. 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, 2013

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

Full ranking

Rank	Counties	2013 (%)	Change on 2012
1	Johnson County	98.1	+5.8 pts
2	Platte County	96.6	+3.2 pts
3	Carbon County	96.4	+20.1 pts
4	Park County	95.2	+9 pts
5	Lincoln County	92.6	+6.5 pts
6	Sheridan County	89	+3.2 pts
7	Big Horn County	85.9	-11.9 pts
8	Uinta County	85.5	+16.1 pts
9	Teton County	83	+14.1 pts
10	Natrona County	82.5	-1.6 pts
11	Converse County	80.8	-1.4 pts
12	Weston County	80	-20 pts
13	Sublette County	74.8	+22.9 pts
14	Laramie County	74.2	+12.7 pts
15	Fremont County	71	+12.5 pts
16	Sweetwater County	68.8	+11.4 pts
17	Albany County	64.6	+16.4 pts
18	Campbell County	56.2	+21.2 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 2013 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 Wyoming by share of days with good air quality (US EPA AQI), 2013) [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 Wyoming by share of days with good air quality (US EPA AQI), 2013. 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/wyoming-counties?period=2013. 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 Wyoming by share of days with good air quality (US EPA AQI), 2013. 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/wyoming-counties?period=2013.

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 Wyoming by share of days with good air quality (US EPA AQI), 2013 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/wyoming-counties?period=2013 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_wyoming_by_2013,
  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 Wyoming by share of days with good air quality (US EPA AQI), 2013}},
  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/wyoming-counties?period=2013. 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 Wyoming by share of days with good air quality (US EPA AQI), 2013
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/wyoming-counties?period=2013
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wyoming-counties?period=2013.
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)?

Johnson County, with 98.1% in 2013, according to EPA.

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

Campbell County, with 56.2% in 2013.

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 2013 and are not ranked.