December in Jena averages a daily high of 5.3°C with nights around -0.1°C. Expect roughly 14.7 wet days totalling 41.4mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Jena is May–September.
Based on JENA STERNWARTE, GM (0.5km), 1995–2024. 30 years of December data.