Like us humans, cats are sensitive to Uv radiation. Certain body parts are exposed a lot and are therefore more vulnerable.
For cats, these are particularly the ears and bridge of the nose. There the fur is thinner and blocks less radiation.
Cats love to lie on their backs and warm their bellies in the sun. Since the belly coat is not as dense as the back coat, the belly can also burn quickly.
During hot temperatures, make sure your cat stays calm and always has a place in the shade to cool off. Consider a bath, sprinklers or a cardboard box in a cool place. Your furry friend can't resist this and so he is not in the draft. After all, cats don't like that.