Farther south on the Peninsula, the San Andreas Fault cuts through the range, producing the Crystal Springs gap, partly occupied by San Francisco’s Crystal Springs reservoirs. The breeze through the gap causes Redwood City and other Peninsula cities to be a bit less warm in summer than it would be minus the gap. The cooling effect sometimes extends as far south as San Jose.
The marine air may drop the temperature only slightly, but a few degrees can make a big difference in comfort. You might be quite happy sitting outside at 68 degrees, but if a breeze drops the temperature to 65 you would probably want to move indoors. On a warm summer afternoon in inland areas, you could be comfortable in your home at 80, but at 85 might want to switch on the air conditioner – unless you’re a conscientious conserver of energy and can hold out till the mercury climbs to 95 or 100.