The dog howling in the middle of the night may be something around it, such as movement outside the home or other dogs barking next door, the family dog will bark, this is a normal situation. Because of physical discomfort, such as distemper, pancreatitis, etc., the dog will always bark.
If the dog is cold, hungry, and wants to urinate and defecate in the middle of the night, they will howl, and the owner only needs to meet their needs. If the dog has been locked in the cage for a long time, the dog will be very unconvinced and keep barking.