I start early, 7:00 AM if possible. If you can get things done the night before, do it. Anything you can do to help with shade will give some relief as well. Even if your only standing two feet into the garage with the brew gear right outside of that, it helps.
Things you can do the night before:
Mill grains
Prep brewing equipment
Make a batch of sanitizer and keep it ready
Get notes ready, and recipe ready and easily available
Pre measure hops into solo cups, and mark time on them, then store in the fridge until needed.
Advanced items:
Mash the night prior to brew day. There is a good writeup in the technique in several places. Check Gordon Strong's writeup for, "The Overnight Oven Mash." this will save a TON of time on the brew day, so you'll finish before its too hot.