March in Napa averages a daily high of 19.6°C with nights around 6.3°C. Expect roughly 9.6 wet days totalling 89.5mm. 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 March data.