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

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

Garfield County had the highest share of days with good air quality (US EPA AQI) of 16 counties in 2023, at 100%. Salt Lake County had the lowest, at 40.8%. The median was 64%. Source: EPA.

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Highest100Garfield County
Lowest40.8Salt Lake County
Median6416 counties

Map of counties, 2023

Box Elder County: 83.9 %Cache County: 60 %Carbon County: 90.6 %Davis County: 57.8 %Duchesne County: 49.3 %Garfield County: 100 %Grand County: 55.2 %Iron County: 84.7 %Salt Lake County: 40.8 %San Juan County: 74.8 %Tooele County: 67.9 %Uintah County: 42.2 %Utah County: 55.1 %Washington County: 79.7 %Wayne County: 98.3 %Weber County: 59.7 %
  • Under 55
  • 55 to 60
  • 60 to 75
  • 75 to 85
  • 85 and over
  • No data
%, 2023. 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, 2023

Garfield County: 100 %Garfield County100Wayne County: 98.3 %Wayne County98.3Carbon County: 90.6 %Carbon County90.6Iron County: 84.7 %Iron County84.7Box Elder County: 83.9 %Box Elder County83.9Washington County: 79.7 %Washington County79.7San Juan County: 74.8 %San Juan County74.8Tooele County: 67.9 %Tooele County67.9Cache County: 60 %Cache County60Weber County: 59.7 %Weber County59.7Davis County: 57.8 %Davis County57.8Grand County: 55.2 %Grand County55.2Utah County: 55.1 %Utah County55.1Duchesne County: 49.3 %Duchesne County49.3Uintah County: 42.2 %Uintah County42.2Salt Lake County: 40.8 %Salt Lake County40.8Garfield County: 100 %Garfield County100Wayne County: 98.3 %Wayne County98.3Carbon County: 90.6 %Carbon County90.6Iron County: 84.7 %Iron County84.7Box Elder County: 83.9 %Box Elder County83.9Washington County: 79.7 %Washington County79.7San Juan County: 74.8 %San Juan County74.8Tooele County: 67.9 %Tooele County67.9Cache County: 60 %Cache County60Weber County: 59.7 %Weber County59.7Davis County: 57.8 %Davis County57.8Grand County: 55.2 %Grand County55.2Utah County: 55.1 %Utah County55.1Duchesne County: 49.3 %Duchesne County49.3Uintah County: 42.2 %Uintah County42.2Salt Lake County: 40.8 %Salt Lake County40.8
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2023 (%)Change on 2022
1Garfield County100+16 pts
2Wayne County98.3+2.4 pts
3Carbon County90.6+2.4 pts
4Iron County84.70 pts
5Box Elder County83.9-10.8 pts
6Washington County79.7+0.8 pts
7San Juan County74.8-9 pts
8Tooele County67.90 pts
9Cache County60-1.1 pts
10Weber County59.7+3.5 pts
11Davis County57.8+0.3 pts
12Grand County55.2n/a
13Utah County55.1-1.3 pts
14Duchesne County49.3-11.8 pts
15Uintah County42.2-24.1 pts
16Salt Lake County40.8+13.1 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 2023 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 Utah by share of days with good air quality (US EPA AQI), 2023) [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 Utah by share of days with good air quality (US EPA AQI), 2023. 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/utah-counties?period=2023. 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 Utah by share of days with good air quality (US EPA AQI), 2023. 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/utah-counties?period=2023.

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 Utah by share of days with good air quality (US EPA AQI), 2023 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/utah-counties?period=2023 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_utah_by_2023,
  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 Utah by share of days with good air quality (US EPA AQI), 2023}},
  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/utah-counties?period=2023. 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 Utah by share of days with good air quality (US EPA AQI), 2023
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/utah-counties?period=2023
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/utah-counties?period=2023.
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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Rank Counties in Utah by share of days with good air quality (US EPA AQI) using official data, and cite the source.
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Questions

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

Garfield County, with 100% in 2023, according to EPA.

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

Salt Lake County, with 40.8% in 2023.

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 2023 and are not ranked.

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

Counties in Utah: more rankings