| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 39°F | 29°F | 2.7" |
| February | 19°F | 40°F | 29°F | 3.0" |
| March | 28°F | 49°F | 38°F | 3.5" |
| April | 38°F | 62°F | 50°F | 4.0" |
| May | 48°F | 73°F | 60°F | 3.3" |
| June | 57°F | 79°F | 68°F | 5.0" |
| July | 63°F | 85°F | 74°F | 3.9" |
| August | 60°F | 82°F | 71°F | 4.1" |
| September | 54°F | 77°F | 65°F | 3.7" |
| October | 43°F | 66°F | 54°F | 4.4" |
| November | 33°F | 54°F | 43°F | 3.4" |
| December | 26°F | 44°F | 34°F | 4.0" |
| Index | Willimantic | 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. |
| Mansfield Center, CT | 1,367 | 33 | 34.0% |
| Colchester, CT | 5,147 | 33 | 34.0% |
| South Woodstock, CT | 1,031 | 33 | 34.0% |
| South Coventry, CT | 1,413 | 33 | 34.0% |
| Brooklyn, CT | 1,128 | 33 | 34.0% |
| Willimantic, CT | 18,669 | 33 | 34.0% |
| City | Population | Air Quality Index | National Avg. |
| Augusta, ME | 18,662 | 28 | 44.0% |
| Cedar Mill, OR | 18,661 | 38 | 24.0% |
| Petawawa, ON | 18,660 | n/a | |
| Homewood, IL | 18,656 | 55 | 10.0% |
| Point Pleasant, NJ | 18,686 | 41 | 18.0% |
| Willimantic, CT | 18,669 | 33 | 34.0% |
Here are the best places to live in Connecticut
Most Dangerous Cities In The US
Check out the 10 most dangerous cities in Connecticut
These are the largest cities in Connecticut