Be aware of what should not be put into the moving truck.
Candles in a moving truck driving through the desert in the summer will melt all over your other stuff; carry them with you instead. Leather upholstered furniture will “sweat” if wrapped in plastic; use a pad instead. Things like stamp collections and expensive artwork should travel in your air conditioned vehicle too. It's always a good idea to keep vital documents with you so they aren't lost in the sea of boxes should you need to produce them in a hurry. Planning ahead to keep vulnerable items out of the heat will keep them intact. These are all also things that should go into climate control storage units rather than standard storage.
Be kind to the movers - they’re hot too.
Have cold water available for the packing crew. Respect their needs to take reasonable breaks, especially if it’s uncomfortably hot. Ordering pizzas or providing subs is a nice gesture of goodwill that goes a long way.
Think about air conditioning at both ends of the move.
The doors to your home will be open for extended periods of time and the temperature inside will reflect the temperature outside. Prepare accordingly, remembering that you will literally pay the price if your air conditioners run for hours on end. Keep ceiling fans running and windows open if you opt to forgo the a/c. Also, be sure that the electricity is turned on in the new home because it's going to be hot there too.
Plan for pets and kids.
Make arrangements for your pets and kids. Work out a way to keep them away from the movers. It's best to have a friend or family member take care of them offsite. The movers will need full access to the house and the easier it is for them to move about the quicker the process will go.