December in Santa Rosa averages a daily high of 14.8°C with nights around 4.3°C. Expect roughly 13.2 wet days totalling 179.9mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Santa Rosa is May–October.
Based on SANTA ROSA, CA US (1.7km), 1995–2024. 23 years of December data.