Mine are eating less and drinking more, which is good. They come inside for meals and I make them stay in for a bit to cool off, even though they don't think they need A/C.
Domesticated cats do prefer warmer climes, but when it gets as hot an humid as it does 'round here, it doesn't hurt to make sure they stay in a cooler place for a while. Now that hot weather's upon us, cats will groom themselves more to get rid of the winter coat, so when they go outside, they eat grass, which helps them.....well....."purge" all that fur they swallow.
That can be helped by adding fish oil to their dry food, if they won't eat canned food. Those gel capsules work sufficiently.
Also, if you keep them inside, in A/C, they will find somewhere that is warmer if they get cold; clothes dryers, water heater closets, clothes closets, cupboards. I found my cat in the non-running dryer one day; just laying there with a 'damn, ya found me' expression.