Silicon Valley Microclimates Explained

I’d like to start  by sharing some good news about Santa Clara County. We were recently ranked the HAPPIEST county in California! That’s 1st out of 58 total counties for the state, according to Smart Asset’s 2018 Edition of Happiest Places in America. Not only was Santa Clara County ranked first in California, it made top ten for the United States as a whole! Smart Asset compared U.S counties across eight factors, such as unemployment rate, poverty rate, affordability ratio, marriage rate, divorce rate, bankruptcy rate, life expectancy, and physical activity rate. If you’re curious about where they got their data and how they put it together, be sure to click the link above.

Being acknowledged as the #1 county in the state of California is particularly great news considering how the US fared in this year’s World Happiness Report, a separate annual publication conducted on behalf of the United Nations. The United States fell four spots to 18th this year. The World Happiness Report is a far more comprehensive look at happiness and general satisfaction around the globe, ranking 156 countries by their happiness levels, and 117 countries by the happiness of their immigrants. Our drop to 18th came as a bit of a surprise this year.

While there are certainly pros and cons to where we live, it’s good to know our little neck of the woods is doing alright. Let’s go back to the report in which our county came out on top – Smart Asset’s research highlights Santa Clara County’s good year-round weather and high social metrics. We also have the seventh-highest life expectancy in the country and roughly 85% of residents are physically active — no doubt a result of our terrific weather.

These survey results made think – can our climate have that much of an impact on general satisfaction? I often comment on what a beautiful day it is, and truthfully, I along with many Bay Area residents probably take it for granted. So, scientifically-speaking, how DOES the Silicon Valley climate come to be?

If you google “Silicon Valley weather” (like I did) you’ll get a slew of 10-day forecasts and a boilerplate statement about how the region experiences an average of 300 days of sunshine, along with a breakdown of average temps for each month of the year. A cursory glance shows mostly 60’s & 70’s — pretty good.

I’m by no means a meteorologist, but here’s what a little scientific digging turned up: the Santa Clara Valley is a large flat basin between a set of hills. To the west, are the Santa Cruz mountains and a set of foothills to the east. During the day, the valley ground is warmed by the sun, as the air above it heats up it expands, rises like a balloon which creates a low-pressure area over the valley. The low pressure sucks in the cool air cruising over the cold waters of the Pacific Ocean.
As the air passes over the mountain range and down into the valley, it cools, reducing its ability to hold water vapor so moisture in the air condenses, turning it into fog or clouds.

If the valley low is weak cool air has a harder time making it over the hills resulting in those finger like tentacles of fog creeping over the the skyline ridge. The closer we are to the coast and the lower the mountain range, the more likely we are to experience a blanket of fog. If you think about the topography of the Bay Area, areas closest to the water (such as San Francisco) have little to no barrier. Which is why the Peninsula and South Bay are often much warmer. Cities sandwiched comfortably between the two mountain ranges block much of the ocean air.

Helpful hint: look at what direction the wind is blowing. If it’s coming from the west (the ocean side) this usually means cool ocean air is being sucked into the valley. If the wind appears to be blowing from the east, typically there’s a high pressure area over the valley pushing warm air outward.

So far this is high level overview of the science stuff, but it can get much more complex. Other localized variables affect microclimates – which the Bay Area is known for. For instance, older neighborhoods with mature trees are shadier and cooler and can absorb or block wind. Western facing slopes are warmer than their eastern-facing counterparts, and in downtown San Jose, tall buildings create cool, shady microclimates to the north; and some reflect enough solar radiation to significantly warm areas to the south and west. Towns such as Santa Clara, Sunnyvale, and East Palo Alto are heavily influenced by the Bay and can experience strong winds in the late afternoon and evening. It’s all very fascinating and part of what makes living in the Silicon Valley such a treat. Depending on what type of weather you like best — there’s likely a microclimate to match.

Rather LISTEN than read? Play the audio version below, or subscribe to our weekly PODCAST “Sweet Home Silicon Valley” with Aubrie Aviña on iTunes, or wherever you listen to your favorite podcasts.


Compare listings