Silicon Valley: A Word About the Climate

Silicon Valley Climate - sub-tropical tempsPeople coming from out of the area to relocate to Silicon Valley might not know what to expect from the weather in the San Jose, Santa Clara County, or Silicon Valley Area.  Does this part of California ever rain? How hot is the summer? What is the climate like?

In a nutshell, this is a “sub-tropical” area, or a place that enjoys a mild “Mediterranean climate” that is most heavily influenced by the close proximity of the shoreline and the Pacific Ocean.  Temps are mild, we get little rainfall compared to many parts of the country.

More specifically, we usually get about 10-20 inches of rainfall a year (less on the east and more on the west) and enjoy as many as 300 sunny days a year. Winters seldom see many hard freezes (but they can happen).

A typical summer day has highs in the mid to upper eighties but very low humidity – so it feels much cooler. Heat waves and heat inversions can run the temps up to the low to mid 100s in the hottest parts of the valley. Luckily it doesn’t happen much, or stay for long! Once in awhile, a rare storm in summer will bring high humidity and thundershowers, but for the most part, summers are dry. The hottest month is typically August.

The coldest month, usually, is December. A January day will often have a high in the 60s or 50s, depending. A cold day here is when it does not get into the 50s (not too common). By February, though, the worst is usually over and it’s even possible to have freak warm days that hit 80 degrees!

Our weather varies from year to year. Some years we get drought conditions and may require water rationing . Other years we get lots of wet weather from the Pacific – temps are warmer but there’s much too much rain: those are the El Niño years. Most often, though, winters aren’t that bad – evenings can be nippy as temps drop into the 20s on the worst nights in December or January. It will make the news that people should cover their citrus trees so they aren’t damaged by the freezing temps. (more…)

Sunny Silicon Valley: Sunrise, Sunset, Dawn and Dusk Times

A couple of days ago I made a quick trip to Spokane, Washington, on some family business. As I’m writing this in mid-December, just short of the winter solstice (shortest day of the year), I was struck by how early the sun set and then, the following morning, how late it rose again.  It seemed like I’d “lost” an hour of daylight.

Upon returning home to the San Jose and Los Gatos area (Silicon Valley), I found an awesome site that charts sunrise and sunset (dawn and dusk) times for all of the world.  The link below will take you to the page for San Jose, California, which is a good representation of Santa Clara County and the general Silicon Valley area.

http://www.gaisma.com/en/location/san-jose-california.html

I played with this site awhile, checking the hours of daylight for today going north and south of this area.  It will be the same amount of daylight hours (or very close) during the shortest daylight day of the year, December 21st.  So for people moving around on the west coast, here’s a comparative glimpse on the number of daylight hours during these shortest days of the year:

Hours of daylight during shortest days in Silicon Valley

In summer, of course, it’s the opposite. The further north you go, the longer the days, while the closer to the equator, the shorter the days (and the smaller the swing between summer and winter).

During these “shortest days of the year“, a later sunrise and earlier sunset are really noticed.  In Spokane (about the same as Seattle) the sun is coming up at 7:33 and setting at 3:59pm vs the San Jose area’s 7:16 sunrise and 4:52 sunset (8:26 hours of sun up north vs 9:36 in the south Bay Area – 1 hour, 10 minutes more sun here).

How does this compare to other major cities around the US?  How many hours of sun are they all getting during these darkest days?

Anchorage 5:28
Seattle 8:26
Portland 8:43
Boston 9:05
Chicago 9:08
New York City 9:13
Denver 9:31
San Jose 9:36
Los Angeles 9:53
Atlanta 9:55
Phoenix 9:56
San Diego 10
Miami 10:32
Honolulu 10:50

Seeing the wide differences in sunlight hours alone, I can see why “snowbirds” would migrate south in winter!

Another factor to consider is how much sun you actually see during those hours of daylight!  The San Jose area gets only about 20″ of rain during most years.  Most of our rain comes between November and March or April, but even so, it’s unusual to get rain day after day for more than 3-5 days.  Normally there are sunny and dry days inbetween patches of overcast, drizzle or rain.  The weather will be drier in south county or in the east valley and wetter closer to the coastal foothills (Almaden Valley, Los Gatos, Los Altos).  The Santa Cruz Mountains usually hold back the summer fog, leaving the inland areas sunnier and drier than the coast.

Sometimes the winter fog is “ground fog”, or fog from the Pacific which snakes its way inland through the Golden Gate and inches down the bay southward.  When that happens, you can sometimes go to the top of the Santa Cruz Mountains and enjoy the sunshine while hiking the trails off Skyline Boulevard.

We have 300 sunny days per year in our mild, subtropical climate. Not bad!  Even our winters are not so tough.  As one of my Finnish clients said to me recently, “Mary, you don’t really have winter in San Jose!”