# Counties in Oklahoma by highest daily Air Quality Index (US EPA), 2018

All 25 values come from U.S. Environmental Protection Agency for 2018, so the places are comparable. 20 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/oklahoma-counties

| Rank | Place | index |
|---:|---|---:|
| 1 | Muskogee County | 196 |
| 2 | Tulsa County | 192 |
| 3 | Jefferson County | 151 |
| 4 | Canadian County | 150 |
| 5 | Oklahoma County | 147 |
| 6 | Adair County | 145 |
| 7 | Osage County | 143 |
| 8 | Mayes County | 140 |
| 9 | Love County | 129 |
| 10 | Carter County | 128 |
| 11 | Comanche County | 122 |
| 12 | Cleveland County | 121 |
| 13 | Bryan County | 119 |
| 13 | McClain County | 119 |
| 15 | Creek County | 115 |
| 15 | Dewey County | 115 |
| 17 | Kay County | 114 |
| 18 | Pittsburg County | 108 |
| 19 | Ottawa County | 107 |
| 20 | Custer County | 104 |
| 21 | Nowata County | 97 |
| 22 | Choctaw County | 93 |
| 23 | Sequoyah County | 90 |
| 24 | Washington County | 65 |
| 25 | Le Flore County | 62 |