Watertown, Wisconsin has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3 °C (low) to 13.6 °C (high). Annual precipitation averages 924.8 Millimeters. Watertown is located in USDA Plant Hardiness Zone 5b. 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 | -11.6 °C | -2.8 °C | 36.32 mm |
| February | -10.3 °C | -0.8 °C | 36.58 mm |
| March | -4.3 °C | 5.9 °C | 49.02 mm |
| April | 2.1 °C | 13.4 °C | 92.96 mm |
| May | 8.5 °C | 20.3 °C | 103.89 mm |
| June | 14.2 °C | 25.7 °C | 135.64 mm |
| July | 16.4 °C | 27.8 °C | 108.97 mm |
| August | 15.3 °C | 26.8 °C | 102.62 mm |
| September | 10.8 °C | 23.1 °C | 86.11 mm |
| October | 4.4 °C | 15.7 °C | 74.68 mm |
| November | -1.9 °C | 7.4 °C | 54.1 mm |
| December | -7.8 °C | 0.3 °C | 43.94 mm |
| Annual | 3 °C | 13.6 °C | 924.83 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 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |