I like to say that we have 4 seasons - fires, floods, earthquakes, and mudslides. Only kidding.
Our summer really starts around the middle to the end of July. In August and September itgets very hot (last week in some parts of LA it was 100 deg.) By November it starts to cool down - by that I mean 70's to low/mid 80's during the day and about 50's at night. Winter is our rainy season although lasta year we had very little rain, which is a big problem. The temperature during the day is about high 60's to mid 70's and it is usually clear and smog free since the breezes bow the smog out to the ocean. It is beautiful this time of year. However it does get cold (for Southern California) At night it can go down to the 40's and last year hit freezing in certain parts of Southern CA. I wear wood during the late fall and into the winter. Spring is also very nice, cool - about low 70's, and beautiful.
Hope this helps.