Because the hills, mountains, and large bodies of water produce such vast geographic diversity within this region, the San Francisco Bay Area has a variety of microclimates.
Temperatures near the Pacific Ocean don’t change much during the year. There are cool, foggy summers and mild rainy winters. Inland areas have hotter summers and colder overnight temperatures during the winter. Both are moderate.
San Jose, at the south end the San Francisco Bay, averages less than 15 inches of rain annually, while the Napa Valley at the north end of the Bay averages over 30 inches. Parts of the Santa Cruz Mountains, just a few miles west of San Jose, get over 55 inches of rain!
In the summer, inland regions can be 40 degrees warmer than the coast. This large temperature contrast results in brisk coastal winds. And, strong winds are also produced through gaps in the coastal ranges such as the Golden Gate, the Carquinez Strait, and the Altamont Pass. (The Pass has large wind farms; go look at them.)
The best weather in San Francisco itself is usually from mid-September through mid-October. And, up in the wine country, it’s harvest time. During November into mid-March, winter storms usually last several days. Snow falls on a few San Francisco Bay Area peaks, such as Mount St. Helena, Tamalpais, Diablo and Hamilton. Snow levels range from 1000 feet in Sonoma County to 2,000 ft. in Contra Costa, San Mateo, and Santa Clara counties during the winter. There is just a dusting that looks beautiful lying on the curves on the hills.
Writer: Meredith Blevins, featured travel writer for the Authentic Wine Country. Join her at www.blevinswordworx.com for wine-country mysteries, classes, and the untamed west.