Herndon, Virginia has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 45.5 °F (low) to 65.6 °F (high). Annual precipitation averages 44.6 Inches. Herndon is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 25.1 °F | 42.6 °F | 3.05 in. |
| February | 26.6 °F | 45.9 °F | 2.65 in. |
| March | 33.4 °F | 54.3 °F | 3.8 in. |
| April | 43.6 °F | 66.0 °F | 3.36 in. |
| May | 53.3 °F | 74.2 °F | 4.5 in. |
| June | 62.2 °F | 82.6 °F | 4.43 in. |
| July | 67.1 °F | 87.2 °F | 4.31 in. |
| August | 65.3 °F | 85.5 °F | 3.56 in. |
| September | 58.5 °F | 78.8 °F | 4.28 in. |
| October | 46.2 °F | 67.3 °F | 3.83 in. |
| November | 36.0 °F | 56.4 °F | 3.24 in. |
| December | 29.2 °F | 46.5 °F | 3.58 in. |
| Annual | 45.5 °F | 65.6 °F | 44.59 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7b : 5°F to 10°F |
| Plant Hardiness Zone - 2012 | Zone 7a : 0°F to 5°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |