Thanks for the timely reminder, Joe. In fact now it is most important due to all the snow on the trail. People get double the exposure with the snow reflections.

There is a section in the What can go wrong on Whitney link (in the feature topics box above and left) titled...

Sunshine

Hiked in shorts without sunscreen, sunburn can be very painful. As noted in Wear sunblock, cumulative exposure to sunshine without protection can lead to a number of skin problems, especially in the face area.

Lesson: Wear a wide-brimmed hat and cover up as much of your body as possible while hiking in daylight. Apply sunscreen to the remaining parts of your body, including your ears and around your nose. See Sunscreen Recommendations for more information.

From the "Hiked in shorts without sunscreen", pasadenarehearsal wrote:
An addition to my trip report, I didn't use any sunblock that day and was wearing shorts the whole time. Needless to say, I have a serious burn on my lower legs and am now laying with my swollen feet up, wrapped in bandages from knees to ankles and taking Vicodin for the pain. Feel free to let me know what an idiot I am!!!