I have found having wet hair help some, also wearing one of those neck cooling scarves helps a lot. They say not to freeze the scarf but I still put it in the freezer for 20 minutes to quickly cool them down. When all else fails I will wear damp clothing, or even turn the hose on myself. Now we have air but there were a few weeks last summer we did not or that the air just could not keep up.
A dehumidifier can help too but only to a point.
I just had my first 100% hatch rate. It was only 9 eggs but still after all of the trouble I had with shipped eggs it made my night tonight to come home and see that last one out of the shell.
Woo hoo!!!