May in Napa averages a daily high of 24.9°C with nights around 9.8°C. Expect roughly 3.3 wet days totalling 25.4mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Napa is April–October.
Based on NAPA STATE HOSPITAL, CA US (2.8km), 1995–2024. 29 years of May data.