Gretna, Virginia has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.3 °C (low) to 19.9 °C (high). Annual precipitation averages 1182.1 Millimeters. Gretna is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.2 °C | 8.2 °C | 95.25 mm |
| February | -2.3 °C | 10.3 °C | 72.64 mm |
| March | 1.2 °C | 14.9 °C | 100.08 mm |
| April | 6.3 °C | 20.6 °C | 96.27 mm |
| May | 11.7 °C | 24.6 °C | 111.51 mm |
| June | 16.2 °C | 28.3 °C | 108.2 mm |
| July | 18.7 °C | 30.2 °C | 106.43 mm |
| August | 17.8 °C | 29.3 °C | 96.01 mm |
| September | 14.1 °C | 26 °C | 121.41 mm |
| October | 7.3 °C | 20.7 °C | 89.92 mm |
| November | 1.4 °C | 15.2 °C | 90.17 mm |
| December | -1.6 °C | 9.9 °C | 94.23 mm |
| Annual | 7.3 °C | 19.9 °C | 1182.12 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |