SmogRank / World / North America / United States / New Hampshire
Most polluted cities in New Hampshire, United States
4 measured cities, this year; 3 above the WHO annual guideline. Worst: Keene at 6.2 µg/m³, #2,403 in the world.
Ranked by unhealthy days: the share of each city's measured days with a daily mean over 35.4 µg/m³ (US AQI 101+), Unhealthy for Sensitive Groups or worse on the US EPA's scale. Ties go to the higher average.
Cities coloured by their PM2.5 over the last 24 hours. Fires, smoke and ash: Oct 5, the newest UTC day mapped.
- 1Londonderrylast full day 4 Oct 0%
- 2Keenelast full day 4 Oct 0%
- 3Portsmouth 0%
- 4Laconia 0%
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
Estimated: cities without a monitor
New Hampshire cities we can't measure, with model estimates for the last 7 days. Listed by population, not ranked: estimates aren't precise enough to rank. Model estimates from the Copernicus Atmosphere Monitoring Service (CAMS), adjusted to measured cities nearby where there are any. Adjusted, a single day lands within ×1.5 of what a monitor would read about two times in three; unadjusted, it can be off by half or double. Treat them as a guide, not a measurement.
| City | 7-day estimate |
|---|---|
| Manchester | ≈ 4 µg/m³ |
| Nashua | ≈ 4 µg/m³ |
| Concord | ≈ 4 µg/m³ |
| East Concord | ≈ 4 µg/m³ |
| Derry Village | ≈ 5 µg/m³ |
| Dover | ≈ 4 µg/m³ |
| Rochester | ≈ 4 µg/m³ |
| Salem | ≈ 5 µg/m³ |
| Merrimack | ≈ 4 µg/m³ |
| Derry | ≈ 5 µg/m³ |
| Bedford | ≈ 4 µg/m³ |
Bad-air episodes in New Hampshire
- Northern United States and Canada, July 202614 to 21 July 2026, 8 days327 cities548 µg/m³peak, Superior
- North-eastern United States and Canada, 29 July to 9 August 202512 days292 cities112 µg/m³peak, Marquette
- North-eastern United States and Canada, 24 to 28 July 20255 days113 cities88 µg/m³peak, Sorel-Tracy
- Northern United States and Canada, June 202510 to 14 June 2025, 5 days134 cities71 µg/m³peak, Wilmington
- Northern United States and Canada, May and June 202531 May to 9 June 2025, 10 days247 cities116 µg/m³peak, Nepean
- South-eastern Canada and United States, December 202426 to 29 December 2024, 4 days27 cities48 µg/m³peak, Nepean
Times when many cities around here had PM2.5 at twice their usual or more on the same days.
Use this board
SmogRank, most polluted cities in New Hampshire, United States, PM2.5, this year to 7 Oct 2026, 00:00 UTC, smogrank.com/us/region/new-hampshire?w=year.
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.
Updated 2026-10-07 00:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.