| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 11°F | 32°F | 22°F | 2.1" |
| February | 12°F | 35°F | 23°F | 2.5" |
| March | 21°F | 44°F | 32°F | 2.7" |
| April | 33°F | 60°F | 46°F | 3.2" |
| May | 44°F | 71°F | 57°F | 4.0" |
| June | 53°F | 79°F | 65°F | 5.0" |
| July | 58°F | 84°F | 70°F | 5.4" |
| August | 56°F | 82°F | 68°F | 4.1" |
| September | 50°F | 75°F | 61°F | 3.4" |
| October | 39°F | 62°F | 49°F | 5.5" |
| November | 28°F | 49°F | 38°F | 2.8" |
| December | 19°F | 37°F | 28°F | 3.3" |
| Index | Plainfield | New Hampshire | National |
| Air quality index | 34 | 34 | 42 |
| Pollution index | 5,847,470 | 3,959,618 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 328 |
| Days with moderate air quality | 37 |
| Days w/ poor A.Q. for sensitive groups | |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.180% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Enfield, NH | 2,059 | 34 | 32.0% |
| Newport, NH | 5,530 | 34 | 32.0% |
| Norwich, VT | 621 | 34 | 32.0% |
| Wilder, VT | 3,146 | 34 | 32.0% |
| New London, NH | 1,364 | 34 | 32.0% |
| Plainfield, NH | 265 | 34 | 32.0% |
| City | Population | Air Quality Index | National Avg. |
| Letona, AR | 265 | 45 | 10.0% |
| Lonsdale, AR | 265 | 38 | 24.0% |
| Trinity Center, CA | 265 | 42 | 16.0% |
| Garden Prairie, IL | 265 | 42 | 16.0% |
| Arjay, KY | 265 | 39 | 22.0% |
| Plainfield, NH | 265 | 34 | 32.0% |
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