April in Castro Valley averages a daily high of 18.8°C with nights around 9.6°C. Expect roughly 5.7 wet days totalling 30.6mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Castro Valley is May–October.
Based on HAYWARD AIR TERMINAL, CA US (5km), 1995–2024. 26 years of April data.