Helena, Ohio has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5 °C (low) to 15.6 °C (high). Annual precipitation averages 934.5 Millimeters. Helena 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 | -7.6 °C | 0.7 °C | 61.21 mm |
| February | -6.6 °C | 2.4 °C | 53.85 mm |
| March | -2.2 °C | 7.9 °C | 65.28 mm |
| April | 3.6 °C | 15.3 °C | 92.96 mm |
| May | 10.1 °C | 21.8 °C | 97.03 mm |
| June | 15.5 °C | 27 °C | 96.77 mm |
| July | 17.3 °C | 29 °C | 95.5 mm |
| August | 16.1 °C | 27.8 °C | 86.87 mm |
| September | 12.1 °C | 24.7 °C | 80.01 mm |
| October | 5.9 °C | 17.8 °C | 72.9 mm |
| November | 0.4 °C | 9.8 °C | 69.6 mm |
| December | -4.3 °C | 3.5 °C | 62.48 mm |
| Annual | 5 °C | 15.6 °C | 934.46 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 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |