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

All 30 values come from U.S. Environmental Protection Agency for 2025, so the places are comparable. 10 counties have no value for that period and are not ranked.

- Indicator id: `aqi_good_days_share`
- Unit: %
- Definition: 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.
- Source: 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 (https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual)
- Retrieved: 2026-10-12
- Citation: 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.
- Web page: https://invokely.ai/rankings/good-air-quality-days-share/colorado-counties

| Rank | Place | % |
|---:|---|---:|
| 1 | Jackson County | 98.9 |
| 1 | San Juan County | 98.9 |
| 3 | Routt County | 93.7 |
| 4 | Fremont County | 93.4 |
| 5 | Prowers County | 92.6 |
| 6 | Pitkin County | 92.3 |
| 7 | Alamosa County | 91.5 |
| 8 | Delta County | 85.6 |
| 9 | Archuleta County | 83 |
| 9 | San Miguel County | 83 |
| 11 | Grand County | 79.7 |
| 12 | Gilpin County | 75.8 |
| 13 | Montezuma County | 75.1 |
| 14 | Pueblo County | 73.4 |
| 15 | Gunnison County | 72.5 |
| 16 | Garfield County | 69 |
| 17 | El Paso County | 68.2 |
| 18 | Clear Creek County | 67.9 |
| 19 | Douglas County | 67.7 |
| 20 | Chaffee County | 66 |
| 21 | Mesa County | 65.2 |
| 22 | Park County | 63.1 |
| 23 | La Plata County | 60.8 |
| 24 | Jefferson County | 58.9 |
| 25 | Boulder County | 58.4 |
| 26 | Arapahoe County | 58.1 |
| 27 | Adams County | 55.1 |
| 28 | Larimer County | 50.7 |
| 29 | Denver County | 50.4 |
| 30 | Weld County | 44.7 |