Harpster, Ohio has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.4 °F (low) to 60.2 °F (high). Annual precipitation averages 39.3 Inches. Harpster 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 | 18.7 °F | 33.4 °F | 2.67 in. |
| February | 20.3 °F | 36.2 °F | 2.1 in. |
| March | 28.7 °F | 46.7 °F | 2.69 in. |
| April | 39.2 °F | 60.4 °F | 3.88 in. |
| May | 50.5 °F | 71.5 °F | 4.25 in. |
| June | 60.1 °F | 80.2 °F | 4.42 in. |
| July | 63.2 °F | 83.5 °F | 4.29 in. |
| August | 61.3 °F | 81.9 °F | 3.47 in. |
| September | 53.9 °F | 76.2 °F | 3.23 in. |
| October | 42.9 °F | 63.6 °F | 2.78 in. |
| November | 32.9 °F | 50.0 °F | 2.89 in. |
| December | 24.6 °F | 38.4 °F | 2.65 in. |
| Annual | 41.4 °F | 60.2 °F | 39.32 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 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |