My thoroughbred recently moved to all day turn out. In the past he has been inside during the day and comfortably wore a fly sheet with no sweating issues even in 95+ temps. Now even though he has access to fans and shelter he spends most of his day in the sun.
What is the best fly sheet you have found for high temps and humidity? We live in Charlotte NC so 90+ degrees and 80+ humidity are not uncommon.