It has been in the mid 90's here and they are fine if they have plenty of shade and water. But I will give them watermelon from the fridge, which they love. Also you can pour canned corn into ice cube trays to freeze and give as treats. I have heard of people putting chicken wading pools in their pen. Haven't tried that one. Sounds quite messy if you don't have a large space. But when looking it up there were a few people who take their chickens swimming in their people pool. And they were swimming around. Crazy. Didn't know they could swim. I would be worried their wet feathers would weigh them down.