There are many factors to consider when deciding to leave a dog outside in the cold. First is the breed of the dog and the type of coat it has. You also need to consider how cold the temperature is, along with what type of protection the dog has from the cold. For example, you could never leave a Chihuahua outside in the cold, but a St. Bernard could be quite comfortable outdoors in cooler weather. No animal should be left outside in extreme weather.