Thinking back to when I had horses of my own it got me to thinking of what I did in preparing them for winter.  When the cold winter weather hits, many horse owners right away bring out the horse blankets.  Myself though, I have always figured that a horse’s normal winter coat is much more insulating than a blanket, and unless the horse has been clipped, is outside without a windbreak, or has been moved to a colder climate during the winter months, it will usually actually be warmer without a blanket.
One has to remember that the longer winter coat helps to trap the body heat against the skin. Also, tiny muscles in the skin raise the hairs, creating tiny air pockets which in turn heighten the insulating effect.  So if you flatten their fluffed-up coat by adding layers of light blankets, or even one heavy one, you can actually make the horse colder. Something to think about.  My Opinion Only