Like the Mediterranean, Sonoma Country has wet, mild winters and warm dry summers. Even in the winter, days have a high in the 50's (ºF).  A layer of low clouds and fog often moves inland during the night and retreats in mid-morning.  Summer evenings are usually quite cool. These warm days, cool nights and lack of rain during the growing season that makes for premium wine. The Sonoma wineries tend to be much more spread out. Carneros which includes parts of both Sonoma and Napa and the Russian River areas are cooler while Alexander Valley is a much warmer area.  Others like Dry Creek and Sonoma Valley fall in between weather-wise.

 

 

Sonoma tends to get busier in the summer, especially in the southern part of the county around the town of Sonoma.  Weekdays are better for visiting these areas.  The wineries then to get most crowded after 1pm on the weekends.  Fall weekends are very busy too because people want to come out during the crush (i.e. when the grapes are crushed).  The best time to visit when there is both decent weather and smaller crowds is November or February-March.  The wineries are most quiet during December through March.  The big wine event of the year is the Sonoma County Harvest Fair on the first weekend of October, which attracts tourist fair and wide with booths and events that exhibit Sonoma’s wine, ranching and unique trades.