December in Shiojiri averages a daily high of 6.6°C. Expect roughly 5.8 wet days totalling 44.5mm. Demanding conditions — pack for it and plan indoor options.
Across the year, the best time to visit Shiojiri is May–June.
Based on SUWA, JA (14.6km), 1995–2024. 28 years of December data.