You should blanket your horse in the winter months if you are located in a cold area. You can also blanket your horse on nights before a show in the winter but its mostly recommended you put the horse in an available stall.
You should cover a horse in WINTER
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
All seasons. Summer and Spring have storms, Winter and Fall have cold weather, there is no time a blanket isn't important.
Horses may need blankets during colder seasons such as fall and winter, particularly if they are clipped or have limited shelter. It's important to consider factors such as the horse's breed, coat thickness, and weather conditions when deciding whether to use a blanket. Always monitor your horse for signs of discomfort or overheating when using a blanket.
every other season apart from summer unless it is particularly warm
maybe a sheet for flies in spring but a blanket in winter. depending on where you live.
It depends mainly on where you live but during the winter they should have a heavy blanket and during early spring and late fall they should have a sheet or light blanket.
in spring
You would put a blanket on a horse in the winter to save him from getting a cold or even dieing. However, if you do not clip your horse, it is better to leave him unblanketed. To tell if your horse is cold enough to blanket him, touch his ears. If the are cold, he is most likely cold. If they are not, he is fine as is. Also look for abnormal behavior. If he is standing listlessly with his head down, something is wrong, and it may be that he is cold.
winter
Winter, I would think! Winter, and fall, when cold. Basically, any time when its cold out, kk?