April in Fontana averages a daily high of 23.9°C with nights around 10.6°C. Expect roughly 3.5 wet days totalling 19.5mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Fontana is March–May.
Based on ONTARIO INTERNATIONAL AIRPORT, CA US (13.8km), 1995–2024. 26 years of April data.