Oh, that's true, particularly down in the Silicon Valley. Up in San Francisco, it's probably about 5-10 degrees warmer, because of how the mouth of the Bay impacts things. The summer is the opposite: 5-10 degrees warmer in the SV than up in the City.
And yeah, it can feel kinda cold. Just not real cold. And it probably gets below freezing a couple of days per year. Where I live, maybe one.
I once had the nozzle of my water bottle freeze on my bicycle commute down to Palo Alto. That was a cold morning (but I was dressed for it).