| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 21°F | 36°F | 28°F | 3.9" |
| February | 21°F | 37°F | 29°F | 4.4" |
| March | 29°F | 46°F | 37°F | 7.7" |
| April | 39°F | 59°F | 48°F | 9.6" |
| May | 49°F | 68°F | 58°F | 9.0" |
| June | 57°F | 76°F | 66°F | 12.4" |
| July | 63°F | 81°F | 72°F | 9.8" |
| August | 61°F | 79°F | 70°F | 7.9" |
| September | 55°F | 73°F | 63°F | 6.6" |
| October | 44°F | 62°F | 53°F | 10.7" |
| November | 35°F | 51°F | 43°F | 4.9" |
| December | 27°F | 41°F | 34°F | 3.7" |
| Index | Waterbury | Connecticut | National |
| Air quality index | 41 | 43 | 50 |
| Pollution index | 14,500,300 | 7,127,531 | 5,066,862 |
| 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, State | Population | Air Quality Index | National Avg. |
| Thomaston, CT | 1,803 | 37 | 26% |
| Watertown, CT | 3,351 | 37 | 26% |
| Bethlehem Village, CT | 1,852 | 37 | 26% |
| Oakville, CT | 9,133 | 37 | 26% |
| Bantam, CT | 829 | 37 | 26% |
| Waterbury, CT | 109,211 | 41 | 18% |
| City, State | Population | Air Quality Index | National Avg. |
| Billings, MT | 109,089 | 21 | 58% |
| San Buenaventura (Ventura), CA | 109,067 | 46 | 8% |
| High Point, NC | 108,982 | 40 | 20% |
| Temecula, CA | 108,965 | 89 | 78% |
| Cambridge, MA | 108,757 | 43 | 14% |
| Waterbury, CT | 109,211 | 41 | 18% |
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