Climate
Napa has cool, wet winters and very warm, dry summers. In January, average temperatures range from 57.5 °F (14.2 °C) to 37.9 °F (3.3 °C). In July, average temperatures from range from 82.1 °F (27.8 °C) to 53.0 °F (11.7 °C). There are an average of 25.3 days with highs of 90 °F (32 °C) or higher and an average of 23.4 days with lows of 32 °F (0 °C) or lower. The record high temperature was 113 °F (45 °C) on June 14, 1961. The record low temperature was 14 °F (−10 °C) on December 22, 1990.
Average annual precipitation in Napa is 24.84 inches (631 mm) and there are an average of 64 days annually with measurable precipitation. The wettest year was 1983 with 51.29 inches (1,303 mm) and the dryest year was 1939 with 10.37 inches (263 mm). The most rainfall in one month was 16.13 inches (410 mm) in December 1955, when major flooding occurred in the area. The most rainfall in 24 hours was 5.85 inches (149 mm) on November 21, 1977. Although snow is rare, 1.0 inch fell on March 22, 1987.
