December in Seinäjoki averages a daily high of -1.3°C with nights around -7°C. Expect roughly 15.5 wet days totalling 39.5mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Seinäjoki is June–August.
Based on SEINAJOKI PELMAA, FI (23.3km), 1995–2024. 30 years of December data.