| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 14°F | 33°F | 23°F | 4.0" |
| February | 14°F | 35°F | 24°F | 4.6" |
| March | 23°F | 44°F | 33°F | 6.9" |
| April | 34°F | 59°F | 46°F | 4.4" |
| May | 45°F | 70°F | 57°F | 5.3" |
| June | 54°F | 76°F | 65°F | 5.7" |
| July | 60°F | 82°F | 70°F | 10.6" |
| August | 57°F | 80°F | 67°F | 6.5" |
| September | 50°F | 73°F | 61°F | 8.8" |
| October | 40°F | 62°F | 49°F | 8.2" |
| November | 29°F | 49°F | 39°F | 4.3" |
| December | 21°F | 38°F | 29°F | 4.5" |
| Index | Marlborough | New Hampshire | National |
| Air quality index | 34 | 34 | 42 |
| Pollution index | 6,602,810 | 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 | 0.010% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.060% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Jaffrey, NH | 2,750 | 34 | 32.0% |
| Keene, NH | 22,823 | 34 | 32.0% |
| Winchester, NH | 1,939 | 34 | 32.0% |
| Antrim, NH | 1,364 | 34 | 32.0% |
| Peterborough, NH | 2,704 | 34 | 32.0% |
| Marlborough, NH | 1,093 | 34 | 32.0% |
| City | Population | Air Quality Index | National Avg. |
| Gales Ferry, CT | 1,093 | 37 | 26.0% |
| Bronson, FL | 1,093 | 35 | 30.0% |
| Hector, MN | 1,093 | 32 | 36.0% |
| Division No. 7, Subd. K, NL | 1,093 | n/a | |
| Pala, CA | 1,094 | 64 | 28.0% |
| Marlborough, NH | 1,093 | 34 | 32.0% |
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