April in Sunnyvale averages a daily high of 20°C with nights around 9.4°C. Expect roughly 6 wet days totalling 26mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Sunnyvale is May–October.
Based on MOFFETT FEDERAL AIRFIELD, CA US (4.2km), 1995–2024. 21 years of April data.