December in Gilroy averages a daily high of 16.1°C with nights around 4.1°C. Expect roughly 9.5 wet days totalling 118.6mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Gilroy is April–June.
Based on GILROY, CA US (0.7km), 1995–2024. 23 years of December data.