napa valley average monthly temperature
1 The highest monthly average temperature in Napa for July is 65 degrees. 2  The lowest monthly average temperature in Napa for December is 46 degrees.  The most monthly precipitation in Napa occurs in February with 3.6 inches.
Overall, temperatures are mild in Napa. January is the coldest month, with highs usually in the mid to high 50s. July is the hottest month. While highs can reach into the 100s, the average daily high in July sits around 85.
Throughout the Napa Valley, and especially in Calistoga, you will find al fresco dining, wineries, hiking, shopping, and rejuvenating spa treatments. Spring mornings and evenings are wonderfully crisp, while the days offer pleasant temperatures and abundant sunshine (rainy season is normally over by April 15th).