Personally, I know there's a crapload i don't know about web programming. I do know how to steal a script though
Without looking at the weather site or the WWF homepage, here's what i'd do to steal something like that off another page.
I'd write a (pretty simple) javascript to read the info off the server that serves it to the weather site as frequently as that page does it (probably each time the page gets reloaded). If i wanted to be careful, i'd then copy the data to some encrypted file on the WWF server and display it using a separate javascript. Of course, being that i haven't examined either webpage, i could be 100% off, but once again, i feel the need to stick in my 2 cents where they don't belong.
~Dave