I arrived here last week to attend Monterey Motorsports Classic events which was awesome and staying with my son in Berkeley. You should bring shorts and bring a sweatshirt. Next few days will be in the 80's while at Sonoma but this is NorCal so cool in the early morning and evenings may even get some Bay fog but very low humidity. And of course long pants for track and if cleared anywhere in the grid. It will be perfect weather. But dress for cool at times.