Check the Weather is my new favorite iPhone weather app. It has a very clean design—just a few screens that you can swipe through—but includes the hourly temperature and precipitation information that I care about. It also has extended forecasts for 9 days ahead and supports Dark Sky. The Idlewild font in the initial version really put me off, but with version 1.1 you can choose Helvetica or Futura. Previously, I had used My-Cast for years. I still like it, but Check the Weather requires fewer taps.
Update (2013-01-07): Now that it’s winter, I’ve stopped using Check the Weather. It does not provide any information about the kind or amount of snow to expect.