From Clear Dark Sky comes this fabulous forecast of skywatching conditions. (See the bottom of this page for a more readable, full-size version.) The first row forecasts cloud cover, hour by hour, from white for completely overcast to darkest blue for clear skies. Visit the site for explanations of transparency and seeing. Darkness accounts for moonlight as well as sunlight. The bottom three lines (wind, humidity, temperature) give you an idea how comfortable you might be outside. This would be useful, also, for bird-watching. The forecast is available for thousands of other locations as well.
I'm linking to this forecast at the bottom of my main page. So you'll always be able to see it if you scroll all the way down. I'm tempted to put it at the top. But, face it, not all my readers are that geeky.