Cats yowl at night for many reasons including disorientation, confusion and cognitive issues. Some cats will yowl for no reason at all, which can not only be frustrating but can also be difficult to stop.
As cats age, they experience more pain than they do as young kittens. They also experience mental delusions and ongoing confusion. This means that the cat may cry out due to pain or due to confusion or disorientation trouble throughout the night. The best way to treat crying at night is to take the cat in to the veterinarian. The veterinarian may be able to prescribe medications to temper the crying by addressing the symptoms. In some cases, if there is an underlying medical condition, the condition can be eliminated completely.