I was browsing Johnny's Select Seeds, looking at snap clamps for my greenhouse frame (designed to secure shade cloth/GH film to my metal conduit frames), and found this handy guide to fall planting:
spreadsheet calculator that gives you a good idea on when to plant particular veggies in the summer for your fall harvest. I'd say, from a rough look, half of the items can be planted in July. So I've got to get thinking about it too.
The simple fact is, if you want to harvest throughout the fall, you gotta plant in the summer. Some of the items can be direct sown and others can be started now indoors under grow lights and transplanted. Check out the link via the pic above and start planning your fall garden now. ;-)