My horse is never rugged, even when it drops lower than -30 by Celsium (which is rather common here in winters), and he deals quite nicely. This was also his first winter in a 24/7 pasture, no stalling at all, and he showed no interest in the shelters, having the nice, fuzzy winter coat of his. That's just an example on how well horses can adjust to different weather, if they have the opportunity. The key to warming horses' body is free range quality hay (or grass, I believe you have grass at 23C) and letting their termoregulation to figure it out by themselves.
I have come a long way, to surrender my shadow to the shadow of my horse.