[header] How to protect an outdoor cat from excess sunlight [title] Put feline sunblock on your cat. [step] You can find a waterproof, cat-friendly sunscreen to prevent sunburn. Use one that has an spf of 15 or 30. 
Apply it on areas where the fur is thin, and especially on the extremities of white cats such as the ears and nose. You can buy one at the pet store or ask your vet for a recommendation.