Helvetia, West Virginia has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.4 °C (low) to 15.6 °C (high). Annual precipitation averages 1625.4 Millimeters. Helvetia is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.7 °C | 3 °C | 131.32 mm |
| February | -5.8 °C | 4.8 °C | 121.67 mm |
| March | -1.9 °C | 9.4 °C | 143.26 mm |
| April | 3.7 °C | 16.5 °C | 134.87 mm |
| May | 8.9 °C | 20.8 °C | 166.62 mm |
| June | 13.5 °C | 24.4 °C | 151.89 mm |
| July | 15.4 °C | 26.1 °C | 173.99 mm |
| August | 13.8 °C | 25.8 °C | 131.32 mm |
| September | 11.4 °C | 22.8 °C | 115.32 mm |
| October | 5.1 °C | 17.2 °C | 112.01 mm |
| November | -0.3 °C | 10.7 °C | 106.43 mm |
| December | -3.9 °C | 5.6 °C | 136.65 mm |
| Annual | 4.4 °C | 15.6 °C | 1625.35 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |