| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 21°F | 39°F | 30°F | 2.9" |
| February | 21°F | 40°F | 31°F | 3.1" |
| March | 29°F | 49°F | 39°F | 3.5" |
| April | 40°F | 63°F | 51°F | 4.2" |
| May | 50°F | 73°F | 61°F | 3.8" |
| June | 60°F | 81°F | 70°F | 5.1" |
| July | 66°F | 86°F | 76°F | 4.5" |
| August | 64°F | 84°F | 73°F | 4.1" |
| September | 57°F | 78°F | 67°F | 3.5" |
| October | 46°F | 66°F | 55°F | 5.2" |
| November | 35°F | 54°F | 44°F | 3.3" |
| December | 27°F | 43°F | 35°F | 4.2" |
| Index | Moodus | Connecticut | National |
| Air quality index | 37 | 43 | 42 |
| Pollution index | 4,117,250 | 8,629,883 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 323 |
| Days with moderate air quality | 34 |
| Days w/ poor A.Q. for sensitive groups | 7 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Colchester, CT | 5,147 | 33 | 34.0% |
| Willimantic, CT | 18,669 | 33 | 34.0% |
| South Windham, CT | 1,475 | 33 | 34.0% |
| Niantic, CT | 3,083 | 37 | 26.0% |
| Old Saybrook Center, CT | 1,984 | 37 | 26.0% |
| Moodus, CT | 1,802 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| Remsen, IA | 1,802 | 35 | 30.0% |
| Walcott, IA | 1,802 | 46 | 8.0% |
| Syracuse, KS | 1,802 | 15 | 70.0% |
| Marks, MS | 1,802 | 33 | 34.0% |
| McEwen, TN | 1,802 | 40 | 20.0% |
| Moodus, CT | 1,802 | 37 | 26.0% |
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