# Counties in California by highest daily Air Quality Index (US EPA), 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_max`
- Unit: index
- Definition: Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.
- Source: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: highest daily AQI (https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual)
- Publisher page: https://invokely.ai/en/publishers/environmental-protection-agency
- Retrieved: 2026-10-12
- Citation: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
- Web page: https://invokely.ai/rankings/highest-daily-air-quality-index/california-counties

| Rank | Place | index |
|---:|---|---:|
| 1 | Inyo County | 1,322 |
| 2 | San Bernardino County | 593 |
| 3 | Imperial County | 341 |
| 4 | Plumas County | 253 |
| 5 | Shasta County | 232 |
| 6 | Los Angeles County | 230 |
| 7 | Butte County | 213 |
| 7 | Riverside County | 213 |
| 9 | Tulare County | 185 |
| 10 | Kern County | 177 |
| 11 | Ventura County | 176 |
| 12 | Orange County | 172 |
| 13 | Fresno County | 169 |
| 14 | San Diego County | 161 |
| 15 | Kings County | 156 |
| 16 | Merced County | 151 |
| 17 | Stanislaus County | 150 |
| 18 | Santa Barbara County | 146 |
| 19 | Amador County | 143 |
| 20 | Madera County | 140 |
| 20 | Placer County | 140 |
| 20 | Sacramento County | 140 |
| 20 | San Joaquin County | 140 |
| 24 | Mariposa County | 133 |
| 25 | Nevada County | 132 |
| 26 | Calaveras County | 129 |
| 27 | Del Norte County | 125 |
| 28 | San Luis Obispo County | 122 |
| 29 | Yolo County | 118 |
| 30 | El Dorado County | 115 |
| 30 | Sutter County | 115 |
| 30 | Tuolumne County | 115 |
| 33 | Trinity County | 113 |
| 34 | Santa Clara County | 111 |
| 35 | Tehama County | 109 |
| 36 | Solano County | 107 |
| 37 | Alameda County | 105 |
| 37 | San Benito County | 105 |
| 39 | Contra Costa County | 99 |
| 40 | San Francisco County | 94 |
| 40 | Siskiyou County | 94 |
| 42 | Colusa County | 90 |
| 43 | Humboldt County | 86 |
| 43 | Marin County | 86 |
| 45 | Mendocino County | 83 |
| 46 | Glenn County | 80 |
| 46 | Santa Cruz County | 80 |
| 48 | San Mateo County | 73 |
| 49 | Sonoma County | 72 |
| 50 | Monterey County | 71 |
| 51 | Mono County | 69 |
| 52 | Lake County | 67 |