Smithfield, West Virginia has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.9 °C (low) to 17.8 °C (high). Annual precipitation averages 1287 Millimeters. Smithfield is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.2 °C | 4.2 °C | 101.85 mm |
| February | -5.3 °C | 6.2 °C | 90.68 mm |
| March | -1.8 °C | 11.4 °C | 110.49 mm |
| April | 3.8 °C | 19.1 °C | 104.9 mm |
| May | 9.3 °C | 23.4 °C | 127.25 mm |
| June | 14.2 °C | 27.4 °C | 122.43 mm |
| July | 16.5 °C | 29.2 °C | 141.22 mm |
| August | 15.8 °C | 28.7 °C | 105.41 mm |
| September | 11.7 °C | 25.6 °C | 97.79 mm |
| October | 4.9 °C | 19.1 °C | 88.39 mm |
| November | -0.3 °C | 12.3 °C | 89.66 mm |
| December | -3.7 °C | 6.4 °C | 106.93 mm |
| Annual | 4.9 °C | 17.8 °C | 1287 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| 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 |