Thorntown, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.1 °F (low) to 61.7 °F (high). Annual precipitation averages 42.1 Inches. Thorntown 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 | 18.9 °F | 34.4 °F | 2.83 in. |
| February | 21.5 °F | 38.5 °F | 2.23 in. |
| March | 30.4 °F | 49.5 °F | 3.0 in. |
| April | 41.0 °F | 62.5 °F | 4.22 in. |
| May | 52.2 °F | 73.0 °F | 4.41 in. |
| June | 61.0 °F | 81.2 °F | 5.06 in. |
| July | 64.0 °F | 84.1 °F | 4.51 in. |
| August | 62.0 °F | 82.9 °F | 3.49 in. |
| September | 54.4 °F | 78.1 °F | 3.11 in. |
| October | 43.1 °F | 65.8 °F | 3.17 in. |
| November | 32.9 °F | 51.0 °F | 3.28 in. |
| December | 24.2 °F | 39.2 °F | 2.8 in. |
| Annual | 42.1 °F | 61.7 °F | 42.11 in. |
| 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 : -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 |