| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 20°F | 37°F | 28°F | 5.1" |
| February | 17°F | 36°F | 26°F | 3.8" |
| March | 23°F | 45°F | 34°F | 6.5" |
| April | 36°F | 60°F | 47°F | 11.5" |
| May | 45°F | 69°F | 57°F | 3.6" |
| June | 57°F | 81°F | 68°F | 3.5" |
| July | 62°F | 83°F | 72°F | 3.9" |
| August | 60°F | 84°F | 72°F | 2.8" |
| September | 52°F | 79°F | 65°F | 4.3" |
| October | 46°F | 66°F | 55°F | 10.9" |
| November | 31°F | 53°F | 42°F | 5.4" |
| December | 21°F | 38°F | 29°F | 5.4" |
| Index | Coventry Lake | Connecticut | National |
| Air quality index | 33 | 43 | 42 |
| Pollution index | 2,806,150 | 8,629,883 | 2,726,193 |
| Measurement | Total |
| Days measured | 334 |
| Days with good air quality | 319 |
| Days with moderate air quality | 14 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.004% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.040% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Willimantic, CT | 18,669 | 33 | 34.0% |
| Colchester, CT | 5,147 | 33 | 34.0% |
| Mansfield Center, CT | 1,367 | 33 | 34.0% |
| South Coventry, CT | 1,413 | 33 | 34.0% |
| South Windham, CT | 1,475 | 33 | 34.0% |
| Coventry Lake, CT | 2,135 | 33 | 34.0% |
| City | Population | Air Quality Index | National Avg. |
| Bangor, MI | 2,135 | 39 | 22.0% |
| Navassa, NC | 2,135 | 34 | 32.0% |
| Carlton, OR | 2,135 | 32 | 36.0% |
| Saint-Gervais, QC | 2,135 | n/a | |
| Red Lodge, MT | 2,134 | 21 | 58.0% |
| Coventry Lake, CT | 2,135 | 33 | 34.0% |
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