If the feral cat is able to dig a den under a large pile of branches the cat may be able to keep cool, if they have access to a deck that has a large mass of leaves underneath it the cat can burrow into the leaves and the earth may provide protection from the scorching sun.
Cat lovers and colony caregivers must watch the cats closely and take extra steps to care for the cats. In many cases you will need to provide the cats with shelter and plenty of water.
My neighbor opened his garage door one foot to allow two feral cats an escape from the heat on a day when the heat index reached 104. He told me that the cats hid under his car and drank some water. The feral cats caused no disturbance and exited the garage when the sun set. If you choose to allow the feral and stray cats shelter from the heat in your garage then leave the cats alone. If you enter the area where cats are there they will run away because they are afraid of you or they will climb the walls to try to get away from you. It is best to leave the door open wide enough so cat can come and go. Consider installing a cat door.
Do not attempt to touch the feral or stray cats and keep children and other pets away from them. Remember that they are wild animals and they are afraid of humans, if they are put in an uncomfortable situation they will react by scratching because they are terrified of humans.
It is best to respect the feral cats and provide them with a shelter, a bowl of food and water. Leave the garage door open at a foot so cats can enter or exit. Close your garage at night to prevent wildlife; raccoons, possums or skunks from entering.
Set up a soaking hose in your shade garden and allow it to drip slowly during the late afternoon. A feral cat will lick the water from the hose to keep hydrated. They will also lie in the garden that is being water as it is a way to keep cool.
Lucy’s routine is to lie in my hosta garden.
Outdoor cats are accustomed to heat and thus your air conditioner should not be cold, set it at 86 and the cat will be comfortable.
Here is a YouTube video that will show you how to make an insulated cat house.