Take advantage of the coolest weather service yet, Forecast.io. In your dashboard.
For regular installation, check the releases tab above for the latest version. Do not download the Github generated source.
Flip to the back using the 'i' button and start typing a location name. The most likely latitude and longitude will pop up automatically. If these are good, click 'done'. Enjoy.
This repository tracks the Dashcode project for widget. Dashcode is no longer supported under OS X 10.9, so in order to open the project you'll need to open the Dashcode executable (located in the application package contents) directly.