Horses thrive in temps like 15*C. Mine winter out in minus 30C. Twice in ten years we've had nasty wind/snow/rain at the beginning of winter which can be tough on horses without a shelter. I bo't a good high necked rain sheet, didn't need it but I may. Horses can easily overheat and dehydrate under a blanket in summer. It may help prevent sun fade but that's not a good reason to blanket. Horses have the ability to lift and flatten the hair to help regulate the core temperature. Blanketing inhibits this.