White skies

In most circumstances, white skies are distracting and unattractive.  This is particularly true when shooting landscapes and cityscapes.  Sometimes, though, they are precisely what is needed.  In this shot of a chinstrap penguin in Antarctica, I photographed from a low point of view specifically to include the white sky.  This was a wintry environment, and the white-on-white theme worked perfectly.  You have to be careful about underexposure, of course, because the bright background will influence the meter reading into making the shots too dark.  Therefore, you'll have to use the exposure compensation feature on the camera and set it to + 1 1/3.  Start there and then tweak the exposure as needed.