Yahoo Weather (free) has been my favorite quick-look weather app since it came out a year ago. I believe it looks better than Apple's weather app and provides more information.
Yahoo has posted an updated version, with some worthwhile features. You now get chances of precipitation in the 5- and 10-day forecasts. Wind chill information appears when it is relevant, and there are new animations for moon phases. Another new feature lets you swipe down on the photo to replace it with a new one. It's a small touch, but a nice one.
As before, you can load multiple cities (up to 20) and there is a nice radar map that will pinpoint inclement weather.
There are many weather apps available for iOS, but I think Yahoo Weather provides the most relevant information in a beautiful package. Some apps are specialized with more data and maps, but for the weather highlights, Yahoo Weather is a great choice. The app is multi-lingual, and supports 35 languages.
Yahoo Weather is a universal app that requires iOS 6.0 or later. It is optimized for the iPhone 5.