What is the minimum temperature for a horse to sleep outside?

Answer 1

The answer to this question depends on a lot of different factors. There is not a one size fits all answer here. Horses that are in good body condition (not too thin), with a good winter coat, can handle temperatures outside below zero. This is assuming that the animal can get out of the wind, and that the animal is not too thin and can stay dry. Horses that are thin have a harder time maintaining their core body temperature. Likewise, horses that get wet, horses that have been under artificial lighting and haven't developed a thick winter coat, and horses that have been body clipped have a harder time in the cold. Also, when it is cold and windy, horses have a harder time in the cold. It also depends on what the horse is eating. Horses eating a quality free choice hay are going to produce heat through the digestion of the hay in their hind-gut. Horses have the ability to create heat through the action of their muscles assuming they have ingested a healthy amount of calories. Horses that are hungry have a harder time maintaining body weight. It also depends on what the horse is used to. A horse that is used to being in a warmish barn in a stall is probably going to have a hard time if it is abruptly turned out in the cold.

I have personally had horses outside in -20 deg F temps do just fine if all the factors are right. However, I have also had a horse out in the rain and wind be too cold in temps as warm as 45 deg F. It all depends. If in doubt, keep them inside. Warm horses in good body condition with full bellies are much more pleasant to be around and to work with than thin hungry horses.