This can be normal. Head warmth is not an accurate way to determine if your cat has a fever. Take the temperature rectally to determine if the cat has a fever. A normal temperature is 99.5-102.5 degrees Fahrenheit.
My Cat's Head Feels Slightly Warm When I Pet Her. Is There An Easy Way To Determine If She Has A Fever?
My vet said to feel the backsides of the ears if you don't have a thermometer, if it feels unusually warm than they may have a fever or even an infection in the body.
A dry warm nose is a sign of fever, but the only true way to tell is stick an old fashioned thermometer up the rear end and see.