| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 13°F | 32°F | 22°F | 2.7" |
| February | 14°F | 34°F | 23°F | 2.6" |
| March | 22°F | 43°F | 32°F | 2.6" |
| April | 33°F | 58°F | 45°F | 3.4" |
| May | 45°F | 71°F | 57°F | 4.3" |
| June | 53°F | 77°F | 64°F | 4.9" |
| July | 58°F | 83°F | 70°F | 4.4" |
| August | 56°F | 80°F | 67°F | 4.0" |
| September | 49°F | 74°F | 60°F | 3.4" |
| October | 39°F | 61°F | 49°F | 5.3" |
| November | 28°F | 48°F | 37°F | 2.7" |
| December | 20°F | 37°F | 28°F | 3.7" |
| Index | Charlestown | New Hampshire | National |
| Air quality index | 34 | 34 | 42 |
| Pollution index | 1,843,420 | 3,959,618 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 348 |
| Days with moderate air quality | 17 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.000% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Walpole, NH | 647 | 34 | 32.0% |
| Westminster, VT | 427 | 34 | 32.0% |
| Cavendish, VT | 184 | 34 | 32.0% |
| Perkinsville, VT | 164 | 34 | 32.0% |
| Bellows Falls, VT | 2,908 | 34 | 32.0% |
| Charlestown, NH | 933 | 34 | 32.0% |
| City | Population | Air Quality Index | National Avg. |
| Mi-Wuk Village, CA | 933 | 39 | 22.0% |
| Woods Hole, MA | 933 | 36 | 28.0% |
| Grawn, MI | 933 | 36 | 28.0% |
| Salem, NY | 933 | 35 | 30.0% |
| Brady Lake, OH | 933 | 43 | 14.0% |
| Charlestown, NH | 933 | 34 | 32.0% |
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