# Counties in California by share of days with good air quality (US EPA AQI), 2024

All 52 values come from U.S. Environmental Protection Agency for 2024, so the places are comparable. 6 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/california-counties

| Rank | Place | % |
|---:|---|---:|
| 1 | Lake County | 99.4 |
| 2 | Sonoma County | 95.1 |
| 3 | Mono County | 93.2 |
| 4 | San Mateo County | 88.1 |
| 5 | Marin County | 86.3 |
| 6 | Nevada County | 85.8 |
| 7 | Tuolumne County | 80.8 |
| 8 | Del Norte County | 80.3 |
| 8 | Siskiyou County | 80.3 |
| 10 | Santa Cruz County | 80.1 |
| 11 | Glenn County | 79.8 |
| 11 | Monterey County | 79.8 |
| 13 | Amador County | 78.3 |
| 14 | Solano County | 76.2 |
| 15 | San Francisco County | 76 |
| 16 | Shasta County | 73.2 |
| 17 | Calaveras County | 72.7 |
| 17 | Humboldt County | 72.7 |
| 19 | Trinity County | 72.3 |
| 20 | El Dorado County | 71.3 |
| 21 | San Benito County | 71 |
| 22 | Mariposa County | 69.7 |
| 23 | Tehama County | 68.9 |
| 24 | Mendocino County | 66.7 |
| 25 | Yolo County | 65 |
| 26 | Butte County | 63.1 |
| 27 | Santa Clara County | 55.4 |
| 28 | Contra Costa County | 53.7 |
| 29 | Sutter County | 53.3 |
| 30 | Alameda County | 53 |
| 31 | San Luis Obispo County | 52.7 |
| 31 | Santa Barbara County | 52.7 |
| 33 | Ventura County | 52.2 |
| 34 | Placer County | 51.4 |
| 34 | Plumas County | 51.4 |
| 36 | Sacramento County | 49.7 |
| 37 | San Joaquin County | 48.6 |
| 38 | Merced County | 45.9 |
| 39 | Stanislaus County | 45.4 |
| 40 | Madera County | 44.5 |
| 41 | Orange County | 32.5 |
| 42 | Kings County | 27.3 |
| 43 | Inyo County | 24.6 |
| 44 | Imperial County | 22.7 |
| 45 | Kern County | 20.8 |
| 45 | Tulare County | 20.8 |
| 47 | Fresno County | 19.4 |
| 48 | Colusa County | 18.6 |
| 49 | San Diego County | 12.8 |
| 50 | Riverside County | 11.7 |
| 51 | San Bernardino County | 10.9 |
| 52 | Los Angeles County | 10.4 |