Williamstown, West Virginia has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.7 °C (low) to 18.1 °C (high). Annual precipitation averages 1121.4 Millimeters. Williamstown is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.8 °C | 4.2 °C | 83.82 mm |
| February | -4.9 °C | 6.1 °C | 77.98 mm |
| March | -1.1 °C | 11.5 °C | 102.11 mm |
| April | 4.5 °C | 19.2 °C | 96.27 mm |
| May | 10.2 °C | 23.8 °C | 110.49 mm |
| June | 15.3 °C | 27.9 °C | 119.13 mm |
| July | 17.4 °C | 29.8 °C | 119.89 mm |
| August | 16.8 °C | 29.4 °C | 92.2 mm |
| September | 12.6 °C | 25.9 °C | 86.11 mm |
| October | 5.7 °C | 19.6 °C | 72.14 mm |
| November | 0.3 °C | 12.7 °C | 74.68 mm |
| December | -3 °C | 6.8 °C | 86.61 mm |
| Annual | 5.7 °C | 18.1 °C | 1121.43 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |