December in Yachimata averages a daily high of 12.6°C. Expect roughly 6.5 wet days totalling 65.2mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Yachimata is April–June.
Based on CHIBA, JA (20.4km), 1995–2024. 26 years of December data.