December in Somerville averages a daily high of 6°C with nights around -1.2°C. Expect roughly 11.8 wet days totalling 105mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Somerville is May–September.
Based on BOSTON LOGAN INTERNATIONAL AIRPORT, MA US (8km), 1995–2024. 30 years of December data.