I live in MS where it has been near 100 for a while now. It isn't the "dry" heat that you have in TX, but is humid and thick. I do think that the horses acclimate to the weather, but I still would not work in the middle of the day like that. On occasion, when it is breezy or there is a break in the temps, I will work them.
That's just my .02, my trainer works horses from sunup to sundown, but she makes sure that they are properly cooled and gives electrolytes and gatorade to ensure they stay properly hydrated.
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