Dahlgren, Virginia has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.1 °C (low) to 20 °C (high). Annual precipitation averages 1114.6 Millimeters. Dahlgren is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.2 °C | 7.8 °C | 76.96 mm |
| February | -1.3 °C | 9.3 °C | 70.1 mm |
| March | 2.6 °C | 13.8 °C | 97.28 mm |
| April | 8 °C | 20.2 °C | 81.79 mm |
| May | 13.4 °C | 24.5 °C | 88.65 mm |
| June | 18.3 °C | 29.1 °C | 111.25 mm |
| July | 20.8 °C | 31.4 °C | 105.92 mm |
| August | 19.8 °C | 30.4 °C | 107.19 mm |
| September | 16.3 °C | 27 °C | 104.9 mm |
| October | 9.9 °C | 21.1 °C | 96.01 mm |
| November | 3.9 °C | 14.9 °C | 80.01 mm |
| December | 0.2 °C | 10.1 °C | 94.49 mm |
| Annual | 9.1 °C | 20 °C | 1114.55 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |