I made a little project called PixelWorms, which is a model of a patch of grass in Brighton, England. It uses the aforementioned weather feed to work in real time with the current weather conditions. The pixel earthworms are more likely to appear and reproduce if it is cloudy, night time, or cool outside. Worms are less likely to appear and reproduce if it is overly cold, dry, or hot. If it's raining outside, then the worms show a lot of activity. If it's night time outside, the visuals are meant to (sort of) look like you're viewing the ground through a pair of night vision goggles.
Thanks to Daniel Shiffman for providing an example of how to use the Yahoo! weather feeds.