Even though they're covered in fur, it is possible for cats to suffer from sunburn, just like us. This is especially true of hairless cats, and cats with light-colored fur. Most sunburns that cats get are superficial, however, some can be deeper and more serious. So it's important to be aware of the risks of sunburn, especially for cats that love sleeping on sunny windowsills, or in the sun outside.
Petplace has good descriptions of the different kinds of burns that can affect your cat. Diagnosing sunburn depends on the time of year, and how much time your cat has spent in the sun. Her skin will be red in the burned areas, and she might show signs of discomfort, particularly if you try to touch the burns.
The areas most at risk on your cat, according to Catster, are the tips of her ears, her eyelids, her lips, and the tip of her nose. It's not just the fact that these areas don't have a covering of fur, but also that they don't have much pigment at all. Skin pigment is what protects us from sunburn, and why darker-skinned people don't burn as easily as fair-skinned people. The same is true of cats, and it's why light-colored cats are at higher risk than dark colored cats.
So what can you do, especially if you have a cat that loves going outside? Drs. Foster and Smith recommend using sunscreen that's been developed especially for pets. Like you might for your children, you should try to use sunscreen that's SPF 15 or higher, especially if your cat likes to be outside in the middle of the day. They also recommend using a light t-shirt, or something similar, to cover their skin if their fur is very thin, short, or cut very close to their skin.
If your cat has a sunburn, Petplace recommends taking your cat to the vet to assess how bad the burn is. For superficial burns, your vet will probably want to use topical treatments, like silver sulfadiazine, to ease discomfort and help with healing. He might also want to shave the fur around the burn carefully, to make it easier to treat.
For deeper sunburns, your vet will probably want to hospitalize your cat to re-hydrate her with IV fluids, and to properly clean and monitor the burns for complications. These are deeper-tissue burns, which can be quite serious, even in people. If the burn is bad enough, your cat might lose the parts of him that were injured. If your cat gets a sunburn, especially a bad one, it's a good idea to take her to the vet to determine just how bad it is, and what the appropriate treatment should be.
Cats with sunburns are more likely to develop skin cancer, so it's important that you work to protect your cat's skin from the sun as much as possible, particularly if she's burned before. Prevention is the best medicine for sunburns.