If you don't clip your horse and provide a run-in shelter from wind and rain, 99% of horses will be just fine and better off without a blanket in any season. However, the 1% of unclipped horses and the other horses that are clipped for whatever reason will need one in winter, it provides an extra layer of insulation to keep the horse warm because either it, for some reason isn't able to grow a good enough winter coat or because you robbed him of his natural insulator by clipping him.
I think in the Winter.
winter
if you have trained a horse and it is sweaty you would put a cooler on it, a thin fleece blanket
If your horse shivers from the cold in the winter, you need a blanket. some horses get cold easy other don't. If you live where you don't get snow I would just let your horses grow there extra hair the natural way, but if you live where it snows you should put the blanket on.
If the rider is riding the horse they wear a bridle and a saddle and if they are outside they wear a flymask and / or a fly sheet or nothing and if they're in the stall they will wear nothing or a horse blanket.
The word rug usually means turnout rug which is a waterproof, durable blanket for the horse to wear outside in bad weather. Depending on what region you live in fall through early spring is rug season.
A Large size
Yes, a horse can wear a blanket year round. For cold temperatures, there are blankets of different weights for different temperatures. In the summer, horses can wear an anti-sweat sheet or a fly sheet to keep them clean.
It is bad for horses to wear blankets as you can read in the related link. The only time you would need to blanket a horse is if you rob them of their protection from the cold by clipping them. In this case the blanket is the lesser of 2 evils, even though it is still really bad. To tell if the horse needs a blanket, touch his ears. If they are cold, he is most likely cold. If not, he probably isn't, so leave him unblanketed.
u should only put a blanket on during winter. later fall and early spring u can have a light blanket on. horses do grow there own winter coat that is (don't quote me on this but) 10x warmer than a blanket and you should let them grow that for a little before u put a blanket on them. also younger horses do not need a blanket they should grow there coats out.
Horses should wear blankets in the winter. If they are allowed to grow their winter coats, something light should suffice. However, if they are being used in lessons or showing and get body clipped, it is essential they get a heavy winter blanket. They may also need a light blanket in early spring or late fall, depending on how cold the weather is. Indoors, if the windows are closed or only cracked, they may be fine without a blanket. However, when outside in the winter months, they should always have a blanket on.
kicks