When cats spend a lot of time in cold temperatures they can enter a state that is called hypothermia, in which their body can not regulate their temperature and their central nervous system is affected. Cats usually enter this state when their body temperature is between 90-82 degrees Fahrenheit and everything below that is considered severe hypothermia.
The outside temperature limit can vary, depending on the thickness of the cat’s fur and size. If you have a pet cat, you should know that it is not capable of regulating its temperature as feral cats can, so vets recommend not to leave it outside if the temperatures are below 45 degrees Fahrenheit.
If you do, your cat might have serious health problems like heart and blood flow problems, respiratory problems and can even enter a coma or eventually die. This is why it is important to get an outdoor heating pad for your cat.