I live in the S. CA desert. Last summer temps stayed well over the 100 degree mark, with nights only slightly cooler.
There are hundreds of feral cats in this area and they certainly survive the hot weather. They find shelter under plants that are regularly watered (usually twice a day). The sandy soil seems to contain the cooler temps if the area is in the shade and has water on it.
I have ice packs in the freezer ready to use for my indoor cats should we have problems with the power and/or the AC is out of commission. Me? I use the pool.