December in Kostroma averages a daily high of -4.1°C with nights around -9.3°C. Expect roughly 17.1 wet days totalling 39.7mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Kostroma is May–August.
Based on KOSTROMA, RS (5.9km), 1995–2024. 24 years of December data.