horses are not people, they will grow hair (a winter coat) at the start of winter.

They will survive just fine if they have some sort of wind break and some place they can stand out of the rain/snow, thou even over head shelter isn't that imperiative.

If horses are blanketed before they have a chance to grow their winter coat, you will spend all winter dinking around keeping the blanket on them, so they Don't get cold.

Horses are not people they have survived for thousands of years without a winter blanket on them. There's thousands of wild horses throughout the west living just fine thru the winter and nobody goes out and blankets them.

Granted it takes some time to comb out the winter coat in the spring.