McMullin, Virginia has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 5.1 °C (low) to 18.1 °C (high). Annual precipitation averages 1172 Millimeters. McMullin is located in USDA Plant Hardiness Zone 7a. 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 | -5.2 °C | 6.2 °C | 100.08 mm |
| February | -3.8 °C | 8.4 °C | 81.79 mm |
| March | -0.5 °C | 13 °C | 98.3 mm |
| April | 4.3 °C | 18.4 °C | 103.89 mm |
| May | 8.9 °C | 22.8 °C | 123.44 mm |
| June | 13.8 °C | 26.5 °C | 116.08 mm |
| July | 15.9 °C | 28.2 °C | 113.03 mm |
| August | 15.2 °C | 27.8 °C | 103.63 mm |
| September | 11.7 °C | 25 °C | 82.3 mm |
| October | 4.7 °C | 19.4 °C | 74.93 mm |
| November | -0.8 °C | 13.6 °C | 76.45 mm |
| December | -3.3 °C | 8.3 °C | 98.04 mm |
| Annual | 5.1 °C | 18.1 °C | 1171.96 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 100-125 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 | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |