You'll find with higher temps, a fan is a MUST. Rats that are hot will die easily, become dehydrated easily, and will stop production or have smaller litters.

The best I can say is to use racks because they are well ventilated, get some air moving over them all the time. My rats are miserable at temps in the high 80's, I go through a lot of hoops to keep them cool.
Lots of fans, maybe a swamp cooler if they're effective in TN.