Plymouth, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.5 °F (low) to 59.9 °F (high). Annual precipitation averages 40.4 Inches. 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 | 17.0 °F | 32.0 °F | 2.6 in. |
| February | 19.5 °F | 36.0 °F | 2.37 in. |
| March | 28.1 °F | 47.3 °F | 2.47 in. |
| April | 38.3 °F | 60.2 °F | 3.71 in. |
| May | 49.6 °F | 71.5 °F | 4.37 in. |
| June | 59.3 °F | 80.7 °F | 4.3 in. |
| July | 62.6 °F | 83.7 °F | 4.46 in. |
| August | 60.8 °F | 82.0 °F | 4.03 in. |
| September | 53.2 °F | 76.2 °F | 3.3 in. |
| October | 42.2 °F | 63.6 °F | 3.38 in. |
| November | 32.0 °F | 48.8 °F | 2.99 in. |
| December | 23.1 °F | 37.1 °F | 2.45 in. |
| Annual | 40.5 °F | 59.9 °F | 40.43 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |