December in Yamaguchi averages a daily high of 11.7°C. Expect roughly 11.9 wet days totalling 79.4mm. Demanding conditions — pack for it and plan indoor options.
Across the year, the best time to visit Yamaguchi is April–May.
Based on YAMAGUCHI, JA (2.4km), 1995–2024. 27 years of December data.