A Mediterranean climate best describes the Napa Valley of California.

Warm dry summers and wet cool winters, perfect for growing the award winning grapes used in the wine making, is what you can expect when visiting the area. Rain is rare during the growing season, with most occurring between October and May. January and February are usually the wettest months. The fog which characterizes the region keeps the vines cool and maintains the natural acidity in the fruit. A history of volcanic eruptions and earth movements means that soils are diverse in the area. Summers are always sunny and warm, but never uncomfortable due to the influence of the nearby Pacific Ocean and low humidity levels. Autumn is a spectacular time of the year in the Valley when vines are in full color and it is harvest time.

Historical Weather and Climate Averages

MonthHigh TempLow TempRainfallOcean Temp
January58°F37°F7.46 in.52°F
62°F40°F7.10 in.52°F
March66°F41°F5.31 in.52°F
April73°F44°F1.74 in.51°F
May79°F48°F0.68 in.50°F
June85°F52°F0.17 in.51°F
July89°F53°F0.04 in.52°F
August88°F53°F0.08 in.54°F
September85°F51°F0.41 in.55°F
October77°F47°F1.84 in.55°F
November65°F41°F4.83 in.54°F
December58°F36°F5.22 in.53°F

The following link is to a Napa Valley area website that provides current and historical rainfall, creek and river level monitoring data. This website and the network of rainfall and stream level gage sites is a collaborative project of local Napa County cities, the County of Napa, and the Napa County Flood Control and Water Conservation District. This website is intended to provide information from a network of approximately 50 site locations in the Napa Valley region where weather or stream data collection equipment are located. In this website you will find:

  • Real-time rainfall and other local weather data
  • Current water levels in area creeks and the Napa River
  • Historical data for gage sites operated by Napa County agencies dating back to October 2001 for most locations
  • Ability to view data within multiple map views or view lists of gage sites from the North Bay region down to selected portions of the Napa Valley
  • Graphing and tabular data downloading functions for selectable time periods
  • Links to regional weather and river level forecast sites for up to the minute severe weather and flooding outlook

Napa County Real-Time Rainfall Webpage