Air Quality Rankings for New Hampshire 2026
New Hampshire has 7 cities with EPA air quality data. Belknap, New Hampshire has the cleanest air with a 5-year average AQI of 32. Coos, New Hampshire has the highest AQI at 42.
| # | City | 5yr Avg AQI | Current AQI | Worst Pollutant | Trend | Grade |
|---|---|---|---|---|---|---|
| 1 | Belknap, New Hampshire | 32 | 35 | Ozone | Stable | B |
| 2 | Grafton, New Hampshire | 36 | 37 | Ozone | Improving | B |
| 3 | Merrimack, New Hampshire | 37 | 39 | Ozone | Worsening | C |
| 4 | Hillsborough, New Hampshire | 38 | 39 | Ozone | Stable | B |
| 5 | Cheshire, New Hampshire | 38 | 41 | PM2.5 | Improving | B |
| 6 | Rockingham, New Hampshire | 40 | 40 | Ozone | Improving | B |
| 7 | Coos, New Hampshire | 42 | 43 | Ozone | Stable | B |
Air quality data for New Hampshire is sourced from the EPA Air Quality System (AQS), which monitors outdoor air quality at thousands of stations nationwide.
Frequently Asked Questions
Belknap, New Hampshire has the best air quality in New Hampshire with a 5-year average AQI of 32 and a grade of B.
New Hampshire has 7 cities with EPA air quality monitoring data in our database, covering multiple years of AQI measurements.
The Air Quality Index (AQI) measures five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Lower AQI values indicate cleaner air — 0-50 is "Good," while 150+ is "Unhealthy."
Cities ranked by 5-year average AQI (lower is better). Grades factor in average AQI, trend direction, unhealthy days, and dominant pollutant.