| 2023 Hardiness Zone: | Zone 7b: 5°F to 10°F Zone 7a: 0°F to 5°F | |
| 2012 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7a: 0°F to 5°F | |
| 1990 Hardiness Zone: | Zone 6b: -5F to 0F | |
| Average First Frost Date: | October 11 - 20 | |
| Average Last Frost Date: | April 21 - 30 | |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers | |
| Ecoregion: | 64a - Triassic Lowlands | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | 31 - 45 days Over 86°F |
Annual Climate Data for ZIP Code 20171 - Herndon, VA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 22 | 24 | 32 | 41 | 50 | 59 | 64 | 63 | 55 | 42 | 34 | 26 | 43 |
| Avg Max Temp (°F) | 42 | 46 | 55 | 66 | 75 | 83 | 87 | 86 | 79 | 68 | 57 | 46 | 66 |
| Avg Precip (In.) | 3.12 | 2.74 | 3.58 | 3.21 | 4.21 | 3.91 | 3.65 | 3.75 | 3.92 | 3.36 | 3.31 | 3.13 | 41.89 |