| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 12°F | 35°F | 23°F | 2.8" |
| February | 12°F | 37°F | 25°F | 3.3" |
| March | 21°F | 46°F | 33°F | 3.3" |
| April | 32°F | 62°F | 47°F | 3.8" |
| May | 43°F | 73°F | 57°F | 4.1" |
| June | 52°F | 80°F | 66°F | 5.0" |
| July | 58°F | 85°F | 71°F | 4.4" |
| August | 55°F | 84°F | 69°F | 4.1" |
| September | 48°F | 77°F | 62°F | 3.8" |
| October | 38°F | 64°F | 50°F | 6.5" |
| November | 28°F | 52°F | 39°F | 3.3" |
| December | 18°F | 40°F | 29°F | 4.4" |
| Index | Henniker | New Hampshire | National |
| Air quality index | 27 | 34 | 42 |
| Pollution index | 4,139,320 | 3,959,618 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 360 |
| Days with moderate air quality | 5 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.060% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.020% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Contoocook, NH | 1,353 | 27 | 46.0% |
| Hillsborough, NH | 1,421 | 27 | 46.0% |
| Warner, NH | 638 | 27 | 46.0% |
| Bradford, NH | 306 | 27 | 46.0% |
| Concord, NH | 43,503 | 27 | 46.0% |
| Henniker, NH | 2,566 | 27 | 46.0% |
| City | Population | Air Quality Index | National Avg. |
| Graniteville, SC | 2,566 | 47 | 6.0% |
| Pembroke, GA | 2,565 | 39 | 22.0% |
| Alden, NY | 2,565 | 39 | 22.0% |
| Rhinebeck, NY | 2,565 | 36 | 28.0% |
| Crystal Lake, CT | 2,567 | 40 | 20.0% |
| Henniker, NH | 2,566 | 27 | 46.0% |
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