hi if a cat temperature goes up by just 1 degree over its norm its not good for it they can get a bit robotic when walking. so with a thermometer do this. lubricate the bulb tip with a little petroleum jelly lift the base of the tail and gently slide it into your cat's rectum until half of it is inside. keep it in for three minutes withdraw and check the reading. you should seek veterinary attention if your cat's temperature is under 99°f (37. 2°c) or over 104°f (40°c). hope this helps you. good luck
how to know when cats run fevers