The weather is almost perfect right now... 70s during the day, mid to low 50s at night and in the early morning.
Each night around sunset a fog rolls into most areas and burns off some areas in the afternoon sun...
The curves and mountains of norcal create microclimates, so one hill might be 85 degrees and then next 65. Layer smartly and you should be fine.
Not sure when the rainy season starts exactly, but the weather should continue to be perfect for a little while in the fall.