Watertown, Connecticut has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.9 °C (low) to 15.8 °C (high). Annual precipitation averages 1315.5 Millimeters. Watertown 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.1 °C | 2.2 °C | 90.42 mm |
| February | -7.4 °C | 3.8 °C | 79.25 mm |
| March | -3.5 °C | 8.3 °C | 108.97 mm |
| April | 2.3 °C | 15.2 °C | 101.09 mm |
| May | 8 °C | 21.3 °C | 104.65 mm |
| June | 13.1 °C | 25.9 °C | 117.09 mm |
| July | 16.2 °C | 28.6 °C | 122.68 mm |
| August | 15.3 °C | 27.6 °C | 118.11 mm |
| September | 11.3 °C | 23.6 °C | 119.89 mm |
| October | 4.8 °C | 17.1 °C | 136.65 mm |
| November | -0.4 °C | 10.7 °C | 101.35 mm |
| December | -4.7 °C | 4.8 °C | 115.32 mm |
| Annual | 3.9 °C | 15.8 °C | 1315.47 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |