| | Arnold, MD | McLean, VA | United States |
| Rainfall | 43.7 | 43.8 | 38.1 |
| Snowfall | 13.5 | 20.1 | 27.8 |
| Precipitation Days | 115.9 | 117 | 106.2 |
| Sunny | 210 | 203 | 205 |
| Avg. July High | 87.2 | 86 | 85.8 |
| Avg. Jan. Low | 28.4 | 24.5 | 21.7 |
| Comfort Index (higher=better) | 7.3 | 7.3 | 7 |
| UV Index | 4 | 4 | 4.3 |
| Elevation ft. | 135 | 285 | 2443 |