May in San Francisco averages a daily high of 17.9°C with nights around 10.7°C. Expect roughly 3.7 wet days totalling 17.5mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit San Francisco is June–October.
Based on SAN FRANCISCO DOWNTOWN, CA US (0.8km), 1995–2024. 30 years of May data.