Weatherbug Elite: Check Weather, Avoid Lightning Strikes
The complexity of an app is often based on how much data it collects. Many weather apps just use data from the National Weather Service. Weatherbug Elite, meanwhile, culls from the NWS but also from a sensor network that tracks weather conditions and lightning.
The app also lets you avoid lightning: Set your location and the app can send minute-by-minute reports on lightning strikes near you. This is in addition to the usual forecasts, maps and other weather data. The Elite version ($2.99) recently increased forecast algorithms from seven to 10 days.