Dark Sky is an app for the iPad and iPhone that predicts the weather for your location to the minute. For example a Dark Sky prediction might say that it will start raining in three minutes and then stop raining in half an hour.
Predicting the weather to such a fine degree means that Dark Sky is a great resource for showing weather along a route. The Dark Sky: Weather Along a Traffic Route map does exactly that. The app lets users request directions and then displays the route on a Google Map.
The first 60-minutes of the trip also displays a forecast from Dark Sky, showing where (and how hard) you’ll get rained on if you left right now. The application is just a demo showcasing how the DarkSky API could be combined with the Google Maps API and Dark Sky warn that,
"it lacks features, is not robust, and might behave erratically. Please do not rely on it!"