Simply Weather - is the most informative and most "flat" (in terms of design) weather app in App Store.
Simply Weather will not only please your eyes and wish you a nice day, but also helps to know:
1. Current weather in every city of the world or in your location (geolocation function)
2. 24-hour and 7-day forcast
3. Detailed forcast for each day
Simply Weather uses wether data from weather.io