They need dense shade, damp ground and as much ventilation as possible.
During our near 100° heat wave, I was feeding frozen treats like blueberries, peas and watermelon chunks throughout the day. It is also very advantageous to offer a second water source with electrolytes in it. And always make sure there is lots of fresh clean cool water available. You can put ice cubes in the water.
I also would grab any hen that I could get my hands on that was panting and dunk her in a tote with cool, not cold, water in it and slosh my fingers through her belly feathers to make sure it was getting to her skin. Then I just put her back on the ground and left her soaking wet. All of the hens that had this treatment would stop panting right away and looked much more comfortable. I don't think that would be a good idea with a two week old chick though.