Williamson, West Virginia has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.5 °C (low) to 20.5 °C (high). Annual precipitation averages 1236.7 Millimeters. Williamson is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.6 °C | 7.5 °C | 91.19 mm |
| February | -2.2 °C | 9.8 °C | 89.92 mm |
| March | 1.2 °C | 14.8 °C | 114.81 mm |
| April | 6.6 °C | 21.9 °C | 102.87 mm |
| May | 11.9 °C | 25.9 °C | 118.87 mm |
| June | 16.6 °C | 29.6 °C | 124.97 mm |
| July | 18.7 °C | 31.4 °C | 142.49 mm |
| August | 18.2 °C | 30.9 °C | 100.58 mm |
| September | 14.3 °C | 27.9 °C | 85.34 mm |
| October | 7.5 °C | 21.6 °C | 78.49 mm |
| November | 1.6 °C | 14.9 °C | 77.72 mm |
| December | -1.4 °C | 9.6 °C | 109.47 mm |
| Annual | 7.5 °C | 20.5 °C | 1236.72 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |