Quick...fly mask or no in this heat?

'm going to the barn soon, and can't decide on his fly mask. I took his fly boots off yesterday due to the heat, but should I take his mask off too? It's a Cashel fly mask, so it's well ventilated, but it never gets this hot here so I don't know if he'd be cooler with it off? It's going to hit 100 with high humdity, so heat index is well over 100. I have swat and a mitt to apply fly spray to his nose.