Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Wyoming

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

Platte County had the highest share of days with good air quality (US EPA AQI) of 18 counties in 2018, at 95.1%. Sweetwater County had the lowest, at 57.5%. The median was 78.8%. Source: EPA.

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Highest95.1Platte County
Lowest57.5Sweetwater County
Median78.818 counties

Map of counties, 2018

Albany County: 59.7 %Big Horn County: 89.4 %Campbell County: 70.1 %Carbon County: 80 %Converse County: 84.9 %Fremont County: 68.5 %Johnson County: 83.3 %Laramie County: 78.9 %Lincoln County: 94 %Natrona County: 78.4 %Park County: 91.5 %Platte County: 95.1 %Sheridan County: 66 %Sublette County: 63 %Sweetwater County: 57.5 %Teton County: 74.8 %Uinta County: 78.6 %Weston County: 85.6 %
  • Under 67
  • 67 to 78
  • 78 to 81
  • 81 to 88
  • 88 and over
  • No data
%, 2018. 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, 2018

Platte County: 95.1 %Platte County95.1Lincoln County: 94 %Lincoln County94Park County: 91.5 %Park County91.5Big Horn County: 89.4 %Big Horn County89.4Weston County: 85.6 %Weston County85.6Converse County: 84.9 %Converse County84.9Johnson County: 83.3 %Johnson County83.3Carbon County: 80 %Carbon County80Laramie County: 78.9 %Laramie County78.9Uinta County: 78.6 %Uinta County78.6Natrona County: 78.4 %Natrona County78.4Teton County: 74.8 %Teton County74.8Campbell County: 70.1 %Campbell County70.1Fremont County: 68.5 %Fremont County68.5Sheridan County: 66 %Sheridan County66Sublette County: 63 %Sublette County63Albany County: 59.7 %Albany County59.7Sweetwater County: 57.5 %Sweetwater County57.5Platte County: 95.1 %Platte County95.1Lincoln County: 94 %Lincoln County94Park County: 91.5 %Park County91.5Big Horn County: 89.4 %Big Horn County89.4Weston County: 85.6 %Weston County85.6Converse County: 84.9 %Converse County84.9Johnson County: 83.3 %Johnson County83.3Carbon County: 80 %Carbon County80Laramie County: 78.9 %Laramie County78.9Uinta County: 78.6 %Uinta County78.6Natrona County: 78.4 %Natrona County78.4Teton County: 74.8 %Teton County74.8Campbell County: 70.1 %Campbell County70.1Fremont County: 68.5 %Fremont County68.5Sheridan County: 66 %Sheridan County66Sublette County: 63 %Sublette County63Albany County: 59.7 %Albany County59.7Sweetwater County: 57.5 %Sweetwater County57.5
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2018 (%)Change on 2017
1Platte County95.1+5.1 pts
2Lincoln County94-1.3 pts
3Park County91.5+3.9 pts
4Big Horn County89.4-5.1 pts
5Weston County85.6-3.3 pts
6Converse County84.9+7.6 pts
7Johnson County83.3n/a
8Carbon County80-5.2 pts
9Laramie County78.9+5.7 pts
10Uinta County78.6-6.3 pts
11Natrona County78.40 pts
12Teton County74.8-4.4 pts
13Campbell County70.1+7.4 pts
14Fremont County68.5+0.3 pts
15Sheridan County66-2.5 pts
16Sublette County63+2.7 pts
17Albany County59.7-0.3 pts
18Sweetwater County57.5-13.5 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 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: 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), 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: 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), 2018. 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=2018. 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), 2018. 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=2018.

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), 2018 [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=2018 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_wyoming_by_2018,
  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), 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/good-air-quality-days-share/wyoming-counties?period=2018. 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), 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/good-air-quality-days-share/wyoming-counties?period=2018
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wyoming-counties?period=2018.
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)?

Platte County, with 95.1% in 2018, according to EPA.

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

Sweetwater County, with 57.5% 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: good days as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 3 counties have no value for 2018 and are not ranked.

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

Counties in Wyoming: more rankings