Instructions
Watch for evidence of shivering. A shivering horse is a really, really cold horse. It takes a lot to make most horses shiver. If you see evidence of shivering, bring him inside, throw on a stable blanket and ply him with extra hay.
Keep track of his weight. Rapid weight loss through cold snaps is a sure sign that the food and forage he is getting is not adequate to stoke his internal furnace. While a fat horse does not necessarily mean a warm horse, a thin horse has likely used all his calories in an attempt to warm himself.
Check for dehydration. Keeping track of a horse's water consumption is a good indicator of equine comfort; a frozen horse, like a frozen human, is reluctant to drink. Be sure he is taking in a minimum of eight to 12 gallons of water a day.
How to Determine If My Horse is Warm Enough
Determining whether your horse is warm enough is a tricky proposition for many horse owners; advice and opinions on the subject is widely varied. It would be nice if you could look into his big brown eyes and ask him, and simply listen to the answer. Knowing your horse and his habits well actually does make this possible. He will always tell you what's up, even if he is the most stoic of individuals.