Manassas, Virginia has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.2 °C (low) to 19.1 °C (high). Annual precipitation averages 1082.8 Millimeters. Manassas is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.2 °C | 6.3 °C | 72.39 mm |
| February | -3.4 °C | 8.1 °C | 63.25 mm |
| March | 0.6 °C | 12.8 °C | 88.9 mm |
| April | 6.1 °C | 19.4 °C | 76.45 mm |
| May | 11.6 °C | 23.8 °C | 104.39 mm |
| June | 16.7 °C | 28.7 °C | 110.74 mm |
| July | 19.4 °C | 31.1 °C | 103.12 mm |
| August | 18.2 °C | 30 °C | 95.25 mm |
| September | 14.5 °C | 26.5 °C | 109.98 mm |
| October | 7.5 °C | 20.1 °C | 90.93 mm |
| November | 1.7 °C | 13.9 °C | 80.77 mm |
| December | -1.9 °C | 8.4 °C | 86.61 mm |
| Annual | 7.2 °C | 19.1 °C | 1082.78 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |