Plymouth, 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 15.3 °C (high). Annual precipitation averages 1357.6 Millimeters. Plymouth is located in USDA Plant Hardiness Zone 6a. 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 | -8.3 °C | 1.4 °C | 96.27 mm |
| February | -7.4 °C | 3.1 °C | 83.82 mm |
| March | -3.6 °C | 7.4 °C | 118.11 mm |
| April | 2.2 °C | 15.1 °C | 104.9 mm |
| May | 7.9 °C | 21.1 °C | 107.19 mm |
| June | 13.1 °C | 25.6 °C | 117.35 mm |
| July | 16.1 °C | 28.2 °C | 121.92 mm |
| August | 15.3 °C | 27.2 °C | 119.13 mm |
| September | 11.4 °C | 23.2 °C | 120.65 mm |
| October | 4.9 °C | 16.7 °C | 142.75 mm |
| November | -0.3 °C | 10.1 °C | 105.66 mm |
| December | -5.1 °C | 4.1 °C | 119.89 mm |
| Annual | 3.9 °C | 15.3 °C | 1357.64 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 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |