Do Siamese cats always turn black in winter?

Siamese cats do turn black in winter. This is genetically determined by the Siamese cat itself. The tyrosinase enzyme in its body is less stable and will change with the environment and temperature. Generally, the colder the temperature, the more pronounced the Siamese cat’s melanin gene will be, which is why Siamese cats turn black in winter, while part of their black coat fades to a cream colour in summer.