OK, so last week it was triple digits and the not-yet planted pereniials were fading fast. They'd tip over as I watered, they had to be watered morning and night to keep them fresh and perky... so I had this brilliant idea.
I got the extra plastic totes I have everywhere, because they seem to gather here at night with their mismatched lids that I swear once did match. I put the pereniials in the totes and I could bottom water and they wouldn't fall over and all was right in our scorching dry world.
The next morning the rains started. I was gently tipping the totes over every couple of hours to drain all the excess water that I had been praying for the previous week.
NOW several days later, the totes are just permanently on their sides with the perenials stacked like firewood. They are happy. If silly looking. And it's been too wet to get my truck in the back to unload the compost that would finish a couple of flower beds.
If I were you, I'd probably try to hold things over in pots and plant them out in the fall when weather gets cooler. TN has hot enough summers even in a normal year that I expect you will have a less than ideal success rate with plants that get planted out now unless they're going somewhere very shady or you spend a lot of time rigging up shade for them. Even if you get a cooler spell, the plants won't have time to get established before hot weather comes back.
I do this every year--I can never resist buying things at the nurseries during the summertime, but I keep them in their pots until fall. I put them in a shadier area than they would be in if they were in the garden, that helps keep watering frequency down a bit if they're not sitting out in the afternoon sun.