I am from the midwest and that is currently where my lovely lady is. She is 15.3hh and roughly 1300 lbs. She a solid thoroughbred. Luckily for me, she is also a notorious drinker. She will take as many water breaks from eating as she likes and always takes a drink after riding. Of course we also have an industrial strength fan hanging in the corner of her stall and, being a dark bay with a white nose that tends to burn, she is on mostly night turnout.

It seems to do the job. Occasionally if it's been a really hot day and I've seen her sweating or if we had a harder workout, I would give her an ounce of electrolyte powder. But other than that she is a happy horse and hasn't been really affected by the heat too much.

I give my guy loose salt in addition to his salt block, mixed with a little oats. He eats more salt that way. I set up a little bit of a spray from the sprinkler near his pen when it's really hot, so he can move closer or away if he wants to cool off. Generally he tolerates the heat pretty well, but then he's an Arab so he should. And he has a white coat, no pink skin, and some access to shade if he wants it. He prefers cool fresh water if available, so I provide some in the shade, instead of just in a large trough. We ride in the  early morning to beat the heat , I don't do well in the heat either.