Counties in Utah by share of days with good air quality (US EPA AQI), 2025

Wayne County had the highest share of days with good air quality (US EPA AQI) of 17 counties in 2025, at 97.9%. Salt Lake County had the lowest, at 33.2%. The median was 65.8%. Source: EPA.

Highest97.9Wayne County

Lowest33.2Salt Lake County

Median65.817 counties

All counties, 2025

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

Full ranking

Rank	Counties	2025 (%)	Change on 2024
1	Wayne County	97.9	+0.4 pts
2	Garfield County	97.7	+0.2 pts
3	San Juan County	75.9	-1.6 pts
4	Washington County	75.1	-0.9 pts
5	Iron County	74.7	-8.3 pts
6	Tooele County	74.2	+12.2 pts
7	Carbon County	72.3	-3.7 pts
8	Cache County	66	+1 pts
9	Wasatch County	65.8	-24.4 pts
9	Weber County	65.8	-0.6 pts
11	Box Elder County	64.7	+6.2 pts
12	Davis County	63.3	-0.6 pts
13	Grand County	60.2	-2.5 pts
14	Duchesne County	59.7	-1.8 pts
15	Uintah County	58.4	-1.2 pts
16	Utah County	56.4	-1 pts
17	Salt Lake County	33.2	-7.8 pts

Other periods

2025
2024
2023

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. 2 counties with data in other periods have no value for 2025 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), 2025) [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), 2025. 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. 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), 2025. 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.

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), 2025 [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 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_utah_by_2025,
  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), 2025}},
  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. 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), 2025
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
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/utah-counties.
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.

rank_places {"indicator":"aqi_good_days_share","level":"province","within":"Utah","limit":10}
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Questions

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

Wayne County, with 97.9% in 2025, according to EPA.

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

Salt Lake County, with 33.2% in 2025.

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. 2 counties have no value for 2025 and are not ranked.