Do cowboys make babies? Lets get into the way back machine. Riding horses all day with only the heat of the fireplace at night. Working in the cold tending to the ranch from morning to night. Most people are born in August. Ever been to Montana in November? It ain't warm.
I think its a very valid question. If you literally are going to ride when its so cold you will freeze them, take the car by all means. Ride on a warmer day.