Jamestown, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.7 °C (low) to 16.3 °C (high). Annual precipitation averages 1107.4 Millimeters. Jamestown 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 | -7.3 °C | 1.4 °C | 74.42 mm |
| February | -5.9 °C | 3.6 °C | 62.23 mm |
| March | -0.8 °C | 9.6 °C | 81.53 mm |
| April | 5.1 °C | 16.6 °C | 113.54 mm |
| May | 11.4 °C | 22.5 °C | 119.13 mm |
| June | 16.1 °C | 26.9 °C | 131.06 mm |
| July | 17.8 °C | 28.7 °C | 113.79 mm |
| August | 16.6 °C | 27.9 °C | 84.84 mm |
| September | 12.4 °C | 25.2 °C | 84.07 mm |
| October | 6.2 °C | 18.4 °C | 82.8 mm |
| November | 0.6 °C | 10.3 °C | 86.36 mm |
| December | -4.4 °C | 3.9 °C | 73.66 mm |
| Annual | 5.7 °C | 16.3 °C | 1107.43 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 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 |