As far as I am concerned it's year round sailing season in Southern California. If I don't sail at least twice a month I feel I am neglecting my boat and all that money I am paying for slip fees. As far as extended cruising is concerned, like up to the Channel Islands and up the Coast to San Francisco and beyond. Brian M. Fagan says October is best. I have sailed to Catalina at all times of the year. Once on Thanksgiving and once in February on President's Day. Just watch the weather.