December in Union averages a daily high of 7.4°C with nights around -0.2°C. Expect roughly 11.2 wet days totalling 106.4mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Union is May–June.
Based on NEWARK LIBERTY INTERNATIONAL AIRPORT, NJ US (8.1km), 1995–2024. 30 years of December data.