December in Mountain View averages a daily high of 15.1°C with nights around 5.7°C. Expect roughly 10.9 wet days totalling 61.6mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Mountain View is May–October.
Based on MOFFETT FEDERAL AIRFIELD, CA US (3.8km), 1995–2024. 21 years of December data.