So long as a horse is dry they can handle temperatures down to -40 degrees!
The coldest it usually gets is only -5 to -10 degrees Celsius in Whistler so our horses never get cold. They do well in the cold because they have such massive bodies they can easily keep the heat in. They also grow long thick winter coats that are so insulating they can be covered with snow and it won’t melt! If our horses ever get sweaty working we do put blankets on them after so they don’t chill. Their feet also never get cold even standing in the snow because the outer wall of their hoof is a thick material that doesn’t have any feeling, much like our finger nails.