Keep things watered. This heat is sucking the moisture out of your plants. An inch of rain a week is necessary to replace that moisture and keep your vegetable garden happy and growing. How do you know if we got an inch of rain? The weather person isn't always going to give you specific information for your yard, so take matters into your own hands. Or your own bucket. Make sure it has straight sides (you'll get a more accurate measure of actual rainfall.) Leave it out in the rain; if it's rained in inch, there will be an inch in the bucket. You can take another one of those buckets and drill holes in the bottom: newly planted trees and shrubs need 5 gallons of water twice a week for the first few weeks, so just fill the bucket and let it drain slowly, directly on to the roots.
Stay somewhere cool and shady in this heat. If you're absolutely dying to plant something, plant seeds of squash and beans. Plant them extra deep and pour water in the hole before you put the seeds in. Hold off on planting any new plants until the heat breaks. The plants will thank you for it, and you will thank yourself for it.
Take advantage of holiday sales to stock up on tools. Think about all the things you wish you'd had this spring, and see whether you can find them now at reduced prices. I was surprised to see that some big-box drugstores and even the grocery store also have a selection of cheap yet sturdy hand tools; I'm stocking up on trowels and hand cultivators so I can leave them scattered around the garden. Now I don't have the "no handy tool available" excuse for leaving random pots around the yard unplanted.