Uh, I don't think you want to grab images from someone else's site to incorporate in your own. That kind of thing typically incites a 'cease and desist' letter from an unfriendly legal department.

I think what you want is their RSS Feed (technically you are not supposed to re-use that either, but don't tell anybody I told you). Just use XML::Simple to parse it for what you are looking for and show your own rain images.