Everywhere they live, horses have an opportunity to get too cold or too warm, and owners have an opportunity to underdress or overdress their steeds. We cannot trust local custom to decide when to dress our buddies, because local custom varies so widely from place to place. In the eastern U.S., where I live, it is often colder than we’d like, and horses spend much of the winter season wearing heavy blankets. In the summer, when it is hot, these same horses often wear “fly sheets”, but because fly sheets are not as sturdy as blankets, other horses are more likely to eat them, and most of our horses must endure the flies without assistance. In the western U.S., where winters are usually much…