A linked question would be ‘Why is my cat shivering?’. If your cat is genuinely suffering from low body temperature (hypothermia) the signs are violent shivering. This may be followed (unless the cat warms up) by lethargy and listlessness, collapse and coma. Although you probably can’t measure the cat’s temperature it will be below 97 degrees Fahrenheit. The point I am making is that a cat might be cold as we are sometimes in cold weather but it is not something to be concerned about from a health standpoint but where there is shivering there ware health issues.
If you are searching the internet for information on whether your cat’s body temperature has dropped below normal it might be because your cat has suffered hazardous external conditions such as prolonged exposure to very low temperatures.
Under these conditions your cat might by hypothermic. But if the external temperature is normal and your cat appears to be shivering it might be because she has become very wet or is in shock. It might occur after a long time under aesthetic. Kittens can become hypothermic.
Chilling down is a serious danger to young kittens. In order to help avoid this the kitten box and surrounding area should be at 85 to 90 degrees Fahrenheit (29.4-32.2 degrees Celsius) for the first few weeks. The temperature of the kitten box should be constantly monitored. Kittens also receive heat from their mother, siblings, blankets and perhaps a heat lamp.
The treatment for a cat suffering from hypothermia is to warm her up by wrapping her in a coat or blanket and bringing her inside the home if she is outside. Don’t warm her up with a hair dryer as it can dangerous for the cat.
If she has fallen into water and is wet, she should be thoroughly dried after a warm bath. Thereafter she can be warmed up using warm water packs wrapped in towels which are at temperature of a baby’s bottle. The warm packs should be placed at the cat’s armpits, abdomen and chest. The cat’s rectal temperature should be taken regularly (every 10 mins). It should reach 100 degrees Fahrenheit (37.8 degrees Celsius).
Source: Pages 20-21 and 456 of Cat Owner’s Home Veterinary Handbook 3rd edition.