December in Modesto averages a daily high of 13.7°C with nights around 4.1°C. Expect roughly 9.7 wet days totalling 65.1mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Modesto is April–May.
Based on MODESTO AIRPORT, CA US (4km), 1995–2024. 30 years of December data.