Dark Sky is one of the most accurate weather apps I have ever used. I love their textual forecasts that can predict, down to the minute, when it's going to rain.
Yesterday, the app was updated to version 5 and it's better than ever. Custom weather reports and a new forecast view are my favorite new features.
You should definitely download the app if you haven't already. And if you have an Apple Watch, Dark Sky is the best weather app for it.