Brief and moderate sun exposure (walking under the sun for 15-30 minutes, i.e.,) following the hair transplant should not cause harm to your new hair. But it is best to wear a hat because the skin is still in the healing process. Extensive exposure to the sunlight can cause darkening and thickening of the scar tissue. For this reason, direct sun exposure for the first 6-12 months after the surgery is not recommended. Wearing a hat and putting the sunscreen will be a good option.