# Counties in Indiana by highest daily Air Quality Index (US EPA), 2015

All 39 values come from U.S. Environmental Protection Agency for 2015, so the places are comparable. 14 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/indiana-counties

| Rank | Place | index |
|---:|---|---:|
| 1 | Allen County | 176 |
| 2 | Porter County | 168 |
| 3 | Clark County | 164 |
| 4 | Marion County | 159 |
| 5 | Lake County | 151 |
| 5 | Vigo County | 151 |
| 7 | St. Joseph County | 134 |
| 8 | Vanderburgh County | 133 |
| 9 | LaPorte County | 126 |
| 9 | Wabash County | 126 |
| 11 | Elkhart County | 124 |
| 12 | Bartholomew County | 115 |
| 12 | Greene County | 115 |
| 12 | Posey County | 115 |
| 12 | Warrick County | 115 |
| 16 | Perry County | 112 |
| 17 | Floyd County | 108 |
| 18 | Delaware County | 105 |
| 19 | Brown County | 101 |
| 19 | Howard County | 101 |
| 19 | Jackson County | 101 |
| 22 | Tippecanoe County | 99 |
| 23 | Boone County | 97 |
| 23 | Hancock County | 97 |
| 25 | Hamilton County | 93 |
| 25 | Knox County | 93 |
| 27 | Johnson County | 90 |
| 28 | Madison County | 89 |
| 28 | Whitley County | 89 |
| 30 | Carroll County | 87 |
| 31 | Montgomery County | 83 |
| 32 | Monroe County | 82 |
| 33 | Morgan County | 80 |
| 34 | Dubois County | 79 |
| 35 | Spencer County | 78 |
| 36 | Shelby County | 77 |
| 37 | Henry County | 75 |
| 38 | Huntington County | 71 |
| 39 | Hendricks County | 61 |