Watertown, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 35.6 °F (low) to 54.2 °F (high). Annual precipitation averages 31.7 Inches. Watertown is located in USDA Plant Hardiness Zone 4b. 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 | 5.2 °F | 22.4 °F | 0.81 in. |
| February | 8.6 °F | 27.2 °F | 0.85 in. |
| March | 21.4 °F | 39.7 °F | 1.47 in. |
| April | 34.8 °F | 54.9 °F | 2.86 in. |
| May | 47.7 °F | 67.9 °F | 4.27 in. |
| June | 58.3 °F | 77.5 °F | 4.82 in. |
| July | 62.5 °F | 82.1 °F | 3.97 in. |
| August | 60.0 °F | 79.7 °F | 4.31 in. |
| September | 51.7 °F | 72.4 °F | 3.26 in. |
| October | 38.5 °F | 57.8 °F | 2.39 in. |
| November | 25.6 °F | 41.6 °F | 1.5 in. |
| December | 12.4 °F | 27.6 °F | 1.16 in. |
| Annual | 35.6 °F | 54.2 °F | 31.67 in. |
| 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 4b : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |