There is nothing wrong with drinking hot coffee in the summer. In fact if you aren’t quite to the point of sweating yet, it can be a good thing.
You see, the way our bodies cool is by sweating. The sweat then evaporates from our skin and that is what cools us off. When you drink something hot, your stomach sensors get active and send signals you are hot to your hypothalamus. It then reacts by overcompensating with sweat.
If you are very hot and sweaty already – go ahead and drink your coffee cold because it won’t help.