It is abnormal for kittens to have a body temperature of 40 degrees. This is a sign of fever. The healthy body temperature of kittens is between 38-39°. When the cat’s body temperature is lower or higher than the normal temperature, it is a fever. At this time, the owner can use Use physical methods to help the kitten cool down, or take the cat to the pet hospital for treatment. If the kitten has just entered a new home, stress may cause a high fever. If the kitten has a fever accompanied by diarrhea and vomiting, it means there is a disease in the body.