December in Gießen averages a daily high of 4.6°C with nights around -0.2°C. Expect roughly 15.4 wet days totalling 52.4mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Gießen is May–September.
Based on GIESSEN WETTENBERG, GM (2.3km), 1995–2024. 30 years of December data.