If a cat's nose is simply white, but its nose tip, ear tips, and paw pads feel cold, and the cat is shivering slightly, then it means the cat has caught a cold. Just make sure to keep the cat warm. Generally, a cat's nose will be a little white when it first wakes up. 
Another reason a cat's nose might turn white is because the cat is prone to illness during that period. If a cat has a problem, it will often show up on its nose. Therefore, if we see many cats with white noses, it's likely that the cat is sick.
However, if a cat's nose, gums, and paw pads turn white, it's a clear sign that the cat is anemic. Common causes of anemia in cats include nutritional deficiencies and parasite infections, often occurring in cats that only eat a single type of food, and is even more prevalent in stray cats.
