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

Routt County had the highest share of days with good air quality (US EPA AQI) of 31 counties in 2022, at 100%. Denver County had the lowest, at 44.1%. The median was 76.1%. Source: EPA.

Highest100Routt County

Lowest44.1Denver County

Median76.131 counties

Map of counties, 2022

Under 61
61 to 66
66 to 76
76 to 82
82 to 92
92 and over
No data

%, 2022. 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, 2022

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

Full ranking

Rank	Counties	2022 (%)	Change on 2021
1	Routt County	100	+2 pts
2	Fremont County	97.5	-1.3 pts
3	Pitkin County	96.7	+2.4 pts
4	San Juan County	96.6	+0.8 pts
5	Prowers County	93.2	-2.4 pts
6	Alamosa County	92.2	-2.8 pts
7	Jackson County	91.5	-2.5 pts
8	Pueblo County	90.8	-1.5 pts
9	Delta County	87.4	+6.9 pts
10	Archuleta County	85.8	+12.1 pts
11	Montezuma County	82.2	+5.5 pts
12	Gilpin County	78.4	+9.5 pts
13	Grand County	78.2	+16.3 pts
14	Mesa County	77.3	+9.6 pts
15	Gunnison County	77	+5.2 pts
16	San Miguel County	76.1	+10.6 pts
17	La Plata County	72.9	+7.2 pts
18	El Paso County	68.2	+6.8 pts
19	Clear Creek County	68	+10.3 pts
20	Rio Blanco County	66.6	+8.5 pts
21	Douglas County	66.3	+11.8 pts
22	Park County	65.9	+2.9 pts
23	Arapahoe County	64.9	+4.6 pts
24	Jefferson County	64.1	+3.3 pts
25	Chaffee County	62.8	+20.8 pts
26	Boulder County	61.4	+19.2 pts
27	Garfield County	60.5	+6.3 pts
28	Adams County	49.3	-2.2 pts
29	Larimer County	48.2	+3.3 pts
30	Weld County	46.6	+3.9 pts
31	Denver County	44.1	+9 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. 9 counties with data in other periods have no value for 2022 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 Colorado by share of days with good air quality (US EPA AQI), 2022) [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 Colorado by share of days with good air quality (US EPA AQI), 2022. 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/colorado-counties?period=2022. 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 Colorado by share of days with good air quality (US EPA AQI), 2022. 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/colorado-counties?period=2022.

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 Colorado by share of days with good air quality (US EPA AQI), 2022 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/colorado-counties?period=2022 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_colorado_by_2022,
  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 Colorado by share of days with good air quality (US EPA AQI), 2022}},
  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/colorado-counties?period=2022. 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 Colorado by share of days with good air quality (US EPA AQI), 2022
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/colorado-counties?period=2022
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/colorado-counties?period=2022.
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)?

Routt County, with 100% in 2022, according to EPA.

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

Denver County, with 44.1% in 2022.

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. 9 counties have no value for 2022 and are not ranked.