In my small corner of the world, many streams and falls are surrounded by wooded landscape. I've conditioned myself to be sensitive to lighting, especially when working shots in between the cover of clouds. By the way, don't let clouds or early morning fog cancel your outing plans. Such conditions can produce great results. In fact, given the choice, I'd choose an overcast day over a traditional sun-drenched one for the great detail and softness diffused light can provide to an image.
Open shade can also produce good results with some help from filters and film.
I should note, however, that diffused light does create rather flat and uninteresting skylines. I try to exclude or minimize boring skylines in my compositions whenever possible. Certain films possess characteristics well suited to overcast, diffused, or open shade conditions. Information you can find in the latest film reviews can help narrow the selection process. I find films with a warm balance work best under these circumstances, often eliminating or at least reducing the degree to which I need to warm an image with filters.