When do you scratch due to heat?

[Linny]

Horses take cold far better than heat. I can see scratching because of heat but honestly, if the race is the Belmont and you are that close to a TC...I wouldn't want to opt out either. Tagg knew Funny Cide didn't really like mud and had to face a ton of it in the Belmont. If it's any other race, he probably would have stayed in the barn.