We can’t say it enough: the sunny, warm subtropical climate found in Silicon Valley is a big draw for people wanting to improve their quality of life. Many say that the weather is “Mediterranean”, meaning loads of sunshine, not too much rain, and an environment favorable to palm trees, citrus, and other warmth-loving plants, trees, and bushes. San Jose and the nearby area gets about 15 – 20″ of rain in most years (exceptions are drought years at one end of the spectrum and El Nino wet years at the other).
Summers are usually dry and it’s very unusual to have a rainy summer day. Most of the precipitation falls between November and March or April.
The Pacific Ocean dominates weather patterns here, and to a lesser extent, so does the bay, where the wind can blow unimpeded. The coastal range of mountains are very green as they get more precipitation (the Los Gatos Mountains may get 40 – 44″ of rain per year in places). Areas such as Almaden, Los Gatos, Monte Sereno and Saratoga, closest to the Los Gatos Mountains, get a little more rain. Parts near the eastern foothills, such as Alum rock, get less. Downtown San Jose gets 17 – 18″ of rain per year.
Often a breeze kicks up in the afternoon. It flows stronger by the bay and cools down the areas closest to it. You have probably read that San Francisco is cold in summer, and that’s true – the fog rolls in as nature’s air conditioner when the inland areas are baking under the summer sun. The Peninsula gets some of that fog and wind, but of course to a far, far lesser degree since there are mountains holding back much of that effort from the Pacific Ocean. In general, the Peninsula is much windier than the South Bay. (And as an aside, the North Bay – places like Santa Rosa and Napa – get a ton more rain and harsher weather in winter than we do in the southern part of the Bay Area.)
Newcomers frequently ask me about the difference between Los Gatos and Los Altos, as both are wonderful areas with attractive “downtown” magnets, great schools, beautiful neighborhoods and are generally upscale. Los Gatos is closer to Santa Cruz, it’s located at the base of the Santa Cruz Mountains and is a little warmer in summer than Los Altos, which is closer to the bay (and the peninsula) and gets those cooling breezes. Summer temps may be 5-10 degrees warmer in Los Gatos than Los Altos. Los Altos is noticeably pricier than Los Gatos, too.
What about temperatures? Freezing temps can happen but they are not common. Once in awhile there will be a frost or freeze warning or advisory; when that happens, residents protect sensitive plants and trees as a bad freezing spell can seriously hurt or kill grape vines, citrus, etc. A typical winter day is in the 50s or 60s at the warmest point. A typical summer day is in the 80s – but it should be noted that we do not have much humidity in the summers, so an 88 degree day here is not the same as it would be in Rome, Italy! We have a few very hot (over 100 degree) days each year, but usually less than 2 weeks of that all combined. Many older houses do not have central air conditioning for that reason, though most newer homes do have it and it is often added when houses sell if not already in place.
Overall, the climate in Silicon Valley is fairly similar to what you might find in parts of Italy, France and Spain, depending on the elevation, proximity to the hills or bay. Those coming to California from Mediterranean climates will find the terrain and weather very similar, with many of the same trees, bushes and plants found here too, such as olive trees, palm trees, vineyards, citrus trees, stone fruit, and more. It seems that most homes have a lemon tree and perhaps a few other fruit trees, for instance, even on smaller suburban lots in places like San Jose’s Cambrian Park or in the city of Cupertino, home to Apple Computer and well regarded for its distinctive schools the world over. Something you won’t find in Mallorca, the Cinque Terre or Nice, though – the stunning redwood trees found here and within a 300 mile stretch of the California coastal regions.