Smithfield, Virginia has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 10.9 °C (low) to 20.7 °C (high). Annual precipitation averages 1254.8 Millimeters. Smithfield is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -0.1 °C | 9.3 °C | 89.15 mm |
| February | 0.8 °C | 10.9 °C | 72.9 mm |
| March | 4.4 °C | 14.8 °C | 103.63 mm |
| April | 9.8 °C | 20.7 °C | 93.73 mm |
| May | 15.1 °C | 24.8 °C | 103.63 mm |
| June | 19.8 °C | 29.2 °C | 112.78 mm |
| July | 22.2 °C | 31.4 °C | 123.44 mm |
| August | 21.5 °C | 30.3 °C | 143.51 mm |
| September | 18.3 °C | 27.3 °C | 136.4 mm |
| October | 11.8 °C | 21.8 °C | 97.28 mm |
| November | 5.8 °C | 16.2 °C | 84.58 mm |
| December | 1.9 °C | 11.5 °C | 93.73 mm |
| Annual | 10.9 °C | 20.7 °C | 1254.76 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |