I referred to SF because people know it. I live in Concord which is about 35 miles from SF. If you can stand to read all of this, your confusion should disappear.

Keep in mind that this area isn't EXACTLY like SJ, however it is mild in the SF area.
On some days, it is 65 in SF and 95 in Concord at the very same minute of the day (30 degrees diff). This is a microclimate unlike the east coast where it is pretty much the same temp give or take 5 degrees for hundreds of miles.
There isn't any humility to speak of out here during the day - Concord has something like 27% during the day and then it goes way up during the night. The sun burns the humility out of the air during the day.
The weather here is controlled by the temp of the water in the Bay (around 50 degrees). The air blows over the water and cools things down - especially at night but during the day the further inland you go the more the sun wins (heating things up during the day).
Check Yahoo weather several times a day for Concord, SF, Dublin, San Mateo, Marin and you'll get an idea of what a microclimate is all about.
There is a place a little south of SF, in the hills, that is windy and cold and has fog so thick you can't see 5ft and at the same time it is warm and clear after a 10 minute drive down hill. This is during the day.
Current Concord temp and humidity:
64 degrees, 73% humidity (1:25AM)
Our weather here is mild like in SJ, Costa Rica. The reason a 3 bedroom, 2 bath house that has 1450 sqft in a neighborhood without good schools costs 525,000 is because the weather makes this place a paradise.
I live in an area that has lots of wind so while it is very warm in downtown Concord, it can be 15 degrees cooler at my house. Wind.... there is about 2000 windmills about 2 miles from me.
Since living here (I'm from Maryland), I've turned into a weather whimp! Humidity sucks the energy out of me these days (I'm 42), but the sad thing is that I'm likely going to sell the house and move to Jacksonville soon - I'm stopping there before moving to SJ. Why going to Jacksonville... long story.