The weather info, including images is supplied by The Weather Channel.
In most cases, radar maps are provided by them, and pretty general as to where they show, unless you are changing continents or some countries. (For anywhere Canada, we only see the continent of North America)
If you are not seeing one for a particular location, it would most likely be that the Weather Channel is not returning one to the xWeather plugin.
I am hoping that possibly I could get a copy of the existing xWeather source code, as I would like to add some enhancements to the existing code to possibly select different weather info sources and add alternate images to be able to be displayed.
Hope this helps..
James