Bathing in the winter, especially in the Midwest is a challenge. If you have a heated barn, with warm water and heat then you are very lucky and have nothing to worry about. Most people do not have this luxury. Sometimes you are required to bathe areas of your horses’ body to treat certain skin disease and wounds. If this is the case I would bring warm water to the barn and spot clean the area.
Use whatever cleaning products are necessary and keep none involved areas covered. After cleaning towel dry as much as possible or, in the case of a wound pat dry. You can help to dry the area with more toweling, covering with a leg bandage or in some cases using a hair dryer. Only put your horse back outside when the area is dry, especially if the area is located outside of the blanket. If your horse has a medical condition that needs daily care and your facilities are not appropriate your local veterinary hospital will probably take the horse and manage the condition for you without you having to worry about either you or your horse’s skin freezing.