I have a m/w cob who has grown quite a thick coat. Up until this weekend when I clipped him he hadnt had a rug on at all. He is now in his lightweight and I will move to his medium in Nov and then on to his h/w end dec-feb. It really depends on the type of horse. My shetland has a thick woolly coat and lives out all year with no rug. Whereas my friends tb and arab have been rugged up since september

It's not really a specific temperature, it depends on the individual horse. If your horse is cold, it's time to put a rug on, starting with a light turn-out and progressing to thicker rugs as it gets colder. You can tell if your horse is cold by feeling the base of his ears. If he is cold there, put a rug on. TB's usually feel teh cold more than cobs. If your horse is clipped you must put a rug on. People usually start clipping around now. As a rough guide, all the horses on our yard are now in rugs, except the two cobs, who will be by next weekend. My horse will be in a medium weight from November until Christmas, then he'll go into a heavy weight in Jan and Feb, and possibly March, then back to a medium weight, and so on as the weather gets warmer.