Should I blanked my horse before a horse show night. ( like just a light fly sheet just to keep her clean )

Yes you can use a stable sheet of its not boiling out. But normally it's ok because you would only put it on at night check and take it off early am.
If the fly sheets cool enough for warm weather, that should be totally fine. I used to put a cooler on my horse the night before, but it was always cold so she was okay
I do depending on the weather if it's too hot just pray they don't roll lol
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