WeatherBar is an application written in C# to show the weather in a specific location and it can be integrated in the taskbar of the Windows 7. It takes very low memory and its background can be changed too. Its simple to install and run.

All you have to do is to download WeatherBar from the link given below, install it and edit the settings according to your choice and your Windows 7 operated system will have the ability to change the wallpaper automatically according to the weather.
Visit the below URL to download WeatherBar app --> http://weatherbar.codeplex.com/