Dark Sky
Dark Sky brings you at-the-moment weather. You'll know you have three minutes to make it to the building before the rain starts pouring down. http://geekbeat.tv/darksky-ios
WeatherCaster
WeatherCaster is feature packed, but its UI is uncluttered and simple to browse. Unfortunately it's iPad only, but as they get off the ground, I certainly hope to see it on other platforms! http://geekbeat.tv/weathercaster-ios