# Counties in Utah by highest daily Air Quality Index (US EPA), 2025

All 17 values come from U.S. Environmental Protection Agency for 2025, so the places are comparable. 2 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/utah-counties

| Rank | Place | index |
|---:|---|---:|
| 1 | Salt Lake County | 175 |
| 2 | Uintah County | 126 |
| 3 | Davis County | 119 |
| 3 | Weber County | 119 |
| 5 | Duchesne County | 112 |
| 6 | Utah County | 109 |
| 7 | Carbon County | 108 |
| 7 | San Juan County | 108 |
| 9 | Box Elder County | 105 |
| 9 | Iron County | 105 |
| 9 | Wasatch County | 105 |
| 12 | Tooele County | 101 |
| 13 | Washington County | 97 |
| 14 | Grand County | 96 |
| 15 | Cache County | 87 |
| 16 | Garfield County | 79 |
| 17 | Wayne County | 57 |