When they are sweaty and in the Autumn and winter
You usually put a fleece rug on a horse when you put them outside in the winter. Most horses wont need a winter rug because they grow a thick coat but if it's REALLY cold or your horse is clipped then you will need one.
Winter I should imagine.
On HowrseChaps with fleece
autumn
Fleece sheets are for after exercise to keep the horse from chills while wicking away moisture. They can also be used under stable blankets for added warmth in cold weather.
winter and fall but mostly winter
Winter
it depends on the weather,season, and the kind of blanket
Usually you'd get your horse a new blanket in late fall or early winter. Or what ever the coldest season for your region is.
Winter Horse blankets an be made of fleece, or another heavy fabric, usually waterproof to keep the horse dry!
if you have trained a horse and it is sweaty you would put a cooler on it, a thin fleece blanket
The answer is pretty simple... WINTER!Winter