December in Gaithersburg averages a daily high of 6.6°C with nights around -1.2°C. Expect roughly 10 wet days totalling 97.3mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Gaithersburg is August–October.
Based on DAMASCUS 3 SSW, MD US (13.8km), 1995–2024. 30 years of December data.