Dark Sky. My favorite. It’s also one of the apps that got me back to using iOS after going Android for 8 months. I liked Android, but it just didn’t have the specific apps I wanted. Sure, it had ones close to the apps, but not the exact apps. Dark Sky was one of them.
Also, it’s weather forecast, for our area at least, are usually spot-on. It will tell you it’s going to start raining in the next 20 minutes or whatever. It’s really great.