Well, actually, this is the time to plant fall crops since the heat is finally starting to break -- or SUPPOSED TO BE -- not this year it seems.
If you can find started plants -- broccoli and cabbage, Chinese cabbage, also sow Asian greens and radish (but you will have to put a secure bonnet over them to protect from pests -- if you are using 5 gallon buckets to plant in, I"m wondering if paint strainer bag might work. I bought some to try.)
Theoretically, you should be able to sow fall spinach and fall lettuce now or very soon (after this heatwave breaks).
There are specific varieties of onions that can be started in fall in this climate -- Candy and Walla Walla are two of them, and they should be sown now (or asap). Wait to plant garlic until mid-October.