Bad Air Days in Grafton County, New Hampshire: under 1 a Year
under 1 bad air days a year
Rare: among the cleanest-air counties EPA monitors. Ranked 858 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly particles: smoke and dust (100% particle days).
The bad-air season here
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in July and August. Averaged over 2016 to 2025.
What actually helps here
- Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
- On the odd bad day, check AirNow and keep windows shut.
The record for Grafton
In 2000 to 2009 this county averaged 4 bad days a year; in 2016 to 2025, under 1. The air has improved. The worst recent year was 2025, with 3 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2025-08-05 | 113 | PM2.5 |
| 2025-07-26 | 112 | PM2.5 |
| 2021-07-26 | 106 | PM2.5 |
| 2025-08-04 | 101 | PM2.5 |
| 2023-07-18 | 100 | PM2.5 |
The air on a normal day
Across 3,653 monitored days from 2016 to 2025, the air in Grafton County rated Good on 87% of them, more often than the 72% typical of monitored counties, and Moderate on 13%. The median day sat at AQI 36; one day in ten went above 52.
The pollutant setting the AQI on an ordinary day here:
- ozone62%2,275 days
- fine particles (PM2.5)38%1,378 days
Every recent year on file
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 305 | 57 | 3 | 0 | 36 | 113 |
| 2024 | 366 | 334 | 32 | 0 | 0 | 35 | 80 |
| 2023 | 365 | 311 | 54 | 0 | 0 | 37 | 100 |
| 2022 | 365 | 330 | 35 | 0 | 0 | 36 | 84 |
| 2021 | 365 | 313 | 51 | 1 | 0 | 36 | 106 |
| 2020 | 366 | 344 | 22 | 0 | 0 | 35 | 70 |
| 2019 | 365 | 332 | 33 | 0 | 0 | 35 | 65 |
| 2018 | 365 | 294 | 71 | 0 | 0 | 39 | 90 |
| 2017 | 365 | 294 | 71 | 0 | 0 | 38 | 80 |
| 2016 | 366 | 321 | 45 | 0 | 0 | 36 | 77 |
| 2015 | 365 | 282 | 83 | 0 | 0 | 39 | 90 |
| 2014 | 365 | 282 | 82 | 1 | 0 | 40 | 101 |
| 2013 | 365 | 288 | 77 | 0 | 0 | 38 | 84 |
| 2012 | 366 | 285 | 81 | 0 | 0 | 38 | 97 |
| 2011 | 365 | 254 | 111 | 0 | 0 | 40 | 93 |
| 2010 | 365 | 281 | 84 | 0 | 0 | 38 | 94 |
*2025 may be a partial year in EPA's file.
New Hampshire compared
- Coos County2/yr
- Rockingham County2/yr
- Hillsborough County1/yr
- Cheshire Countyunder 1/yr
- Belknap Countyunder 1/yr
- Merrimack Countyunder 1/yr
How this is counted
A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day.