Days with scattered clouds are the best days to photograph. Having scattered clouds does a couple of things for a composition. First, it gives the sky something to do. Without puffy clouds, the sky is a blank tone. When I was photographing with a large format camera, a blank sky also was an invitation to dust, hair and anything else that would create a white squiggle on a print. Second and more important is that cloudy skies break up the foreground with patches of light and shadow which provide some differentiation in the foreground. Of course all this works only if you are in the right place and have your camera ready for “the decisive moment.” Partly cloudy days are filled with decisive moments and you have to be ready to take advantage of them.