December in Siedlce averages a daily high of 1.8°C with nights around -4.6°C. Expect roughly 13.2 wet days totalling 35.3mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Siedlce is May–September.
Based on SIEDLCE, PL (9.5km), 1995–2024. 17 years of December data.