| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 21°F | 37°F | 28°F | 5.0" |
| February | 19°F | 35°F | 26°F | 9.8" |
| March | 25°F | 44°F | 34°F | 6.0" |
| April | 38°F | 59°F | 47°F | 15.0" |
| May | 46°F | 68°F | 56°F | 14.6" |
| June | 58°F | 78°F | 67°F | 11.3" |
| July | 62°F | 81°F | 70°F | 12.6" |
| August | 62°F | 82°F | 71°F | 8.3" |
| September | 55°F | 76°F | 65°F | 2.3" |
| October | 48°F | 64°F | 54°F | 12.4" |
| November | 34°F | 51°F | 41°F | 5.2" |
| December | 23°F | 36°F | 29°F | 5.5" |
| Index | Derby | Connecticut | National |
| Air quality index | 41 | 43 | 42 |
| Pollution index | 14,500,300 | 8,629,883 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 280 |
| Days with moderate air quality | 71 |
| Days w/ poor A.Q. for sensitive groups | 12 |
| Days with unhealthy air quality | 2 |
| Pollutant | Total |
| Arsenic | 0.030% |
| Benzene | 0.140% |
| Carbon Tetrachloride | 0.050% |
| Lead | 0.080% |
| Mercury | 0.060% |
| City | Population | Air Quality Index | National Avg. |
| Meriden, CT | 59,512 | 41 | 18.0% |
| Wallingford Center, CT | 18,948 | 41 | 18.0% |
| Shelton, CT | 41,162 | 41 | 18.0% |
| Orange, CT | 13,928 | 41 | 18.0% |
| Cheshire Village, CT | 6,491 | 41 | 18.0% |
| Derby, CT | 12,420 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| North St. Paul, MN | 12,421 | 46 | 8.0% |
| Blue Ash, OH | 12,417 | 54 | 8.0% |
| West Monroe, LA | 12,431 | 34 | 32.0% |
| Brock, ON | 12,406 | n/a | |
| Markham, IL | 12,401 | 55 | 10.0% |
| Derby, CT | 12,420 | 41 | 18.0% |
Here are the best places to live in Connecticut
Most Dangerous Cities In The US
These are the 10 cheapest cities in Connecticut
See the best places to live in Derby