January in Vallejo averages a daily high of 14.8°C with nights around 6.4°C. Expect roughly 10.9 wet days totalling 97.7mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Vallejo is April–June.
Based on VALLEJO, CA US (6.1km), 1995–2024. 11 years of January data.