Is everyone in California originally from Ohio? Ai, yi, yi, yi !
It just isn't true that our growing season here on the Central Coast of California is over on September First. Just the opposite - in fact, we have more warm sunny days ahead of us than my old cousins back in Dublin, Ohio had starting in May! We have an incredibly long growing season and, even though we don't have those weeks and weeks of balmy nights, we do have weeks and weeks of frost free growing. So, forget everything your old Midwestern daddy taught you and believe nothing you read on the back of seed packets - plant NOW!
Plant lettuce. It loves cooler climates and sweetens up when the frost sits upon its shoulders. Not freezing weather, but frost, yes! Wonder why we keep lettuce in the refrigerator? It LIKES it!
Plant beets. They get a good start going right now and then those lovely roots sit nicely in colder soil, just waiting to be picked and eaten.
Plant cabbage. You can ignore those monster cabbages that take up all of your garden space and plant the mini-cabbages very close together. Harvest and eat when they are softball sized.
Plant bunching onions. Because you can, year round. Same goes for Chard, Cilantro, Kale of all types, Collards, Broccoli, Brussels Sprouts (long season AND short season), Kohlrabi, Cauliflower - all those brassicas that sweeten in cold weather.
Plant peas - if they grow and produce, fine. If not, they will in spring.
Plant fava beans as an overwintering crop, with garlic, shallots, Walla Walla onions, and Stockton Red onions.
Did I mention Spinach, Chinese cabbage, any and all mustards, Asian greens...
Arugula grows great in winter, so does Cilantro. All the perennial herbs overwinter as do many pepper plants.
Now is NOT the time to stop gardening.