Widgets are small info panels you can have in your home screen:
To create one in Android 4.0 or superior go to the Widgets tab next to the applications one.
In previous Android versions go to HOME window -> Menu button -> Widgets.
In both cases look for UK Weather widgets. There are 3 different ones:
Once you have selected the type of widget you want a configuration window will appear:
Here you can configure:
Once created, you will see the widget in your home screen, and it will update by itself every hour (that's the default time but you can change it in application settings).
But if at any moment you want, you can update manually the widget pressing on a little reload button that is at the top right except for the clock widget that is at the bottom left.
Once you have created a widget you can change it's configuration pressing on it and going to Settings menu option -> Widget (in the Forecasts window).
In the settings window you will also found Background data loading settings that you can use to configure widget update time.