The ultra-violet rays from the sun especially at this time of year can be extremely intense and damaging to the epidermis and into the inside dermis tissue. You may have heard of the various stages or degrees of burn to tissue. The newly implanted follicules are establishing their blood supply, without it they will perish. The soft tissue takes a longer time to heal than the outer tissue. IMO most docs will advise you to avoid direct sun exposure for six to eight months post-op. In addition, many other health professionals like derms will warn against direct exposre to ultra-violet rays for more than seven minutes. The higher the UV rating, the more potential damage that can be done.