| | Greenbelt, MD | Herndon, VA | United States |
| Rainfall | 43.4 | 42.9 | 38.1 |
| Snowfall | 13.2 | 21.5 | 27.8 |
| Precipitation Days | 108.7 | 119.5 | 106.2 |
| Sunny | 199 | 201 | 205 |
| Avg. July High | 87.9 | 85.8 | 85.8 |
| Avg. Jan. Low | 24.1 | 23.5 | 21.7 |
| Comfort Index (higher=better) | 7.3 | 7.3 | 7 |
| UV Index | 4.3 | 4 | 4.3 |
| Elevation ft. | 161 | 361 | 2443 |