Plymouth, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.7 °C (low) to 15.5 °C (high). Annual precipitation averages 1026.9 Millimeters. Plymouth is located in USDA Plant Hardiness Zone 6a. 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 | -8.3 °C | 0 °C | 66.04 mm |
| February | -6.9 °C | 2.2 °C | 60.2 mm |
| March | -2.2 °C | 8.5 °C | 62.74 mm |
| April | 3.5 °C | 15.7 °C | 94.23 mm |
| May | 9.8 °C | 21.9 °C | 111 mm |
| June | 15.2 °C | 27.1 °C | 109.22 mm |
| July | 17 °C | 28.7 °C | 113.28 mm |
| August | 16 °C | 27.8 °C | 102.36 mm |
| September | 11.8 °C | 24.6 °C | 83.82 mm |
| October | 5.7 °C | 17.6 °C | 85.85 mm |
| November | 0 °C | 9.3 °C | 75.95 mm |
| December | -4.9 °C | 2.8 °C | 62.23 mm |
| Annual | 4.7 °C | 15.5 °C | 1026.92 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 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |