Last summer I experienced quite the heatwave with my boy Crusoe. His tank average at about 85 degrees because I have no air conditioner. For a few non-consecutive days it even hit 90 degrees! I did things like freeze pre-conditioned water into ice cubes in a cup that I would float in his tank to try an cool the water but not at too quick a rate. I kept a blanket over the tank to provide shade (he is near but not directly in front of my window) and aim all the fans I owned at the tank.
They can survive surprisingly drastic temperatures. It is not a good idea to keep them in such conditions long term but one in a while will not kill them. I am already making plans on how to deal with this upcoming summer's heat. I certainly do not want to put m boy through that again.