Waterbury, Connecticut has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.6 °C (low) to 16.1 °C (high). Annual precipitation averages 1327.9 Millimeters. Waterbury is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.3 °C | 2.5 °C | 97.79 mm |
| February | -6.7 °C | 4 °C | 84.07 mm |
| March | -2.6 °C | 8.4 °C | 116.08 mm |
| April | 3 °C | 15.3 °C | 106.17 mm |
| May | 8.7 °C | 21.5 °C | 105.41 mm |
| June | 13.8 °C | 26.1 °C | 116.08 mm |
| July | 16.9 °C | 29.1 °C | 114.3 mm |
| August | 16 °C | 28 °C | 111 mm |
| September | 11.9 °C | 24.2 °C | 118.36 mm |
| October | 5.6 °C | 17.6 °C | 136.14 mm |
| November | 0.2 °C | 11.1 °C | 104.9 mm |
| December | -4.1 °C | 5.3 °C | 117.6 mm |
| Annual | 4.6 °C | 16.1 °C | 1327.9 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |