| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 36°F | 26°F | 2.5" |
| February | 18°F | 38°F | 27°F | 3.0" |
| March | 27°F | 46°F | 36°F | 3.6" |
| April | 38°F | 61°F | 49°F | 3.3" |
| May | 48°F | 71°F | 59°F | 3.9" |
| June | 58°F | 79°F | 68°F | 4.6" |
| July | 64°F | 85°F | 74°F | 3.8" |
| August | 61°F | 83°F | 72°F | 4.3" |
| September | 55°F | 76°F | 65°F | 3.9" |
| October | 44°F | 64°F | 53°F | 5.4" |
| November | 33°F | 52°F | 42°F | 3.1" |
| December | 24°F | 40°F | 31°F | 3.6" |
| Index | Londonderry | New Hampshire | National |
| Air quality index | 37 | 34 | 42 |
| Pollution index | 6,602,810 | 3,959,618 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 353 |
| Days with moderate air quality | 12 |
| 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. |
| Amherst, NH | 656 | 37 | 26.0% |
| Haverhill, MA | 63,783 | 37 | 26.0% |
| Derry, NH | 22,891 | 37 | 26.0% |
| Goffstown, NH | 2,848 | 37 | 26.0% |
| Hudson, NH | 7,230 | 37 | 26.0% |
| Londonderry, NH | 12,053 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| Cheval, FL | 12,052 | 43 | 14.0% |
| Festus, MO | 12,054 | 54 | 8.0% |
| Scotts Valley, CA | 12,055 | 35 | 30.0% |
| Brookhaven, MS | 12,045 | 44 | 12.0% |
| Enumclaw, WA | 12,062 | 45 | 10.0% |
| Londonderry, NH | 12,053 | 37 | 26.0% |
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