# Counties in New Hampshire by highest daily Air Quality Index (US EPA), 2003

All 9 values come from U.S. Environmental Protection Agency for 2003, so the places are comparable. 1 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/new-hampshire-counties

| Rank | Place | index |
|---:|---|---:|
| 1 | Hillsborough County | 150 |
| 2 | Belknap County | 147 |
| 2 | Sullivan County | 147 |
| 4 | Grafton County | 140 |
| 5 | Cheshire County | 136 |
| 5 | Rockingham County | 136 |
| 7 | Coos County | 129 |
| 7 | Strafford County | 129 |
| 9 | Merrimack County | 119 |