There are weather app aplenty in the App Store, but some apps reach beyond the typical green blob radar maps and tables of text. Dark Sky offers some unique data presentations, and recently updated to version 2.0 adding some interesting precipitation notifications. The feature will notify you on your phone when it's about to rain or snow. Using push notifications, the app knows your location even if you haven't fired it up in some time. When a storm approaches, you can set a precipitation threshold for notifications and also do not disturb times.
The precipitation notification is still a work in progress and it's currently available in the U.S. Dark Sky is available for both iPad and iPhone/iPod and currently sells for $2.99.