Plymouth, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.8 °C (low) to 12.7 °C (high). Annual precipitation averages 849.4 Millimeters. Plymouth is located in USDA Plant Hardiness Zone 5b. 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 | -11.2 °C | -3.1 °C | 41.4 mm |
| February | -10 °C | -1.2 °C | 36.58 mm |
| March | -4.6 °C | 4.9 °C | 50.04 mm |
| April | 1.4 °C | 11.8 °C | 90.93 mm |
| May | 7.6 °C | 18.4 °C | 100.33 mm |
| June | 13.2 °C | 24.2 °C | 101.35 mm |
| July | 15.9 °C | 27 °C | 91.95 mm |
| August | 15.2 °C | 25.9 °C | 91.19 mm |
| September | 10.7 °C | 22.2 °C | 71.37 mm |
| October | 4.4 °C | 14.7 °C | 74.93 mm |
| November | -1.8 °C | 6.9 °C | 52.83 mm |
| December | -7.5 °C | 0.1 °C | 46.48 mm |
| Annual | 2.8 °C | 12.7 °C | 849.38 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 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |