December in Hamm averages a daily high of 6.7°C with nights around 1.7°C. Expect roughly 16.5 wet days totalling 58.7mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Hamm is May–September.
Based on WERL, GM (12.3km), 1995–2024. 22 years of December data.