Watertown, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.6 °C (low) to 12.8 °C (high). Annual precipitation averages 1112 Millimeters. Watertown is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12 °C | -1.7 °C | 94.74 mm |
| February | -11.6 °C | -0.8 °C | 70.36 mm |
| March | -6.1 °C | 3.9 °C | 71.37 mm |
| April | 1.1 °C | 11.8 °C | 87.88 mm |
| May | 7.9 °C | 19.1 °C | 89.15 mm |
| June | 13.2 °C | 23.7 °C | 90.42 mm |
| July | 16.2 °C | 26.3 °C | 86.36 mm |
| August | 15.3 °C | 25.8 °C | 96.01 mm |
| September | 10.8 °C | 21.9 °C | 96.01 mm |
| October | 4.7 °C | 14.7 °C | 126.24 mm |
| November | -1.2 °C | 7.9 °C | 105.92 mm |
| December | -6.9 °C | 1.4 °C | 97.54 mm |
| Annual | 2.6 °C | 12.8 °C | 1112 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |