April in San Mateo averages a daily high of 18.2°C with nights around 9.7°C. Expect roughly 6 wet days totalling 34.2mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit San Mateo is May–October.
Based on SAN FRANCISCO INTERNATIONAL AIRPORT, CA US (7.2km), 1995–2024. 30 years of April data.