In our area, zone 7 Northeast Oklahoma USA it is still 80 during the sunny days, though in the 50s and 60s at night. The butterflies, skippers, wasps and bees are in their most productive season here - and so are gardeners who love fall and early winter greens from the garden.
Kale, chard, beets and other leafy greens can still be planted and harvested before our first hard freeze. And, with a decent mulch around the roots, salads and sandwich greens often last until January. We've served them at a New Year's Day open house in the past.
Red Russian, Siberian, Lacinato, Blue Curled have all worked well for me in the past - see http://www.seedsavers.org/onlinestore/?search=kale&ext=F
For chards, check out Seeds of Italy's assortment at http://www.growitalian.com/categories/Vegetables/Chard/ - they give you lots of seeds per pack!
Of course, as they say in the investing world, past performance bears no relevance to future performance. For us, that means, Mother Nature can twist and turn at her whim.
Here are some ideas for you if you haven't already planted -
Renee's sale on 2013 seed packets has been extended - Here's a link to that http://www.reneesgarden.com/sale13.htm From the sale list you could still plant lettuce, beets, rapini, chard, peas, radish, mustard, arugula, greens, kale, etc. Also order poppy seeds to plant in November here, etc.
If you like to try broccoli, cabbage and cauliflower, those plants are available in produce markets and garden centers now and would be your best bet. Be sure to put a row cover on them to protect them from flying invasions from destructive insects such as cabbage moths looking for a place to lay eggs.
Also, while you are considering seeds, remember that corn salad, mache, will produce tiny heads in the snow, making lovely individual salad heads for winter meals. Even with a casual planting you'll have half a dozen salads with 2 heads per person for a salad meal when you are missing fresh greens in the dead of winter. http://www.johnnyseeds.com/c-473-corn-saladmache.aspx
And, Botanical Interests reminds us to seed heavily since germination can be spotty - that's my experience, also. http://www.botanicalinterests.com/products/view/3046/Mache-Corn-Salad-Organic-HEIRLOOM-Seeds
Also - how to grow mache
Heirloom Seeds on mache as a gourmet green
lettuce.htm#6022 – MACHE (CORN SALAD) (Valerianella locusta) – 45-50 days – Gourmet salad green, having a very unique, piquant flavor! An old delicious favorite, regaining popularity!
PKT. - 200 seeds - $1.25
PKT. - 200 seeds - $1.25
Seed Library also!
Last spring I saved seeds from the faded green bean plants, dried and replanted them and we're now eating the fresh beans from that planting, so remember to save seeds from your fading fall garden!
For a lovely introduction to early seed saving and sharing before the catalogs don't miss http://americangardenhistory.blogspot.com/2013/09/before-seed-sellers-finding-seeds.html?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+blogspot%2FqxmZp+%28Early+American+Gardens%29