Manually updated using linked file in other comment - PLEASE UPDATE OFFICIAL VERSION... Rated 5 out of 5 stars
Shame TWC doesn't seem to want to update. One star to The Weather Channel, and/or the original author(s) for slacking. 5 stars to the add on itself, and to Silverhawk, for linking an updated file which installs correctly.
The modified .xpi file at the link below works fine. Probably just a quick re-package that modifies a single line of text which says "I can work with Firefox version 'x.123", haven't checked. Easier just to download, for now. Might get the time to experiment some day. It's a pretty easy edit of one text file, and then zipping the file, renaming to '.xpi' extension.
Thanks "Silverhawk" - so dumb that this add on hasn't been "officially" updated. Glad you took the initiative and posted a link.
Now, what would it take for this to simply be "official" so that others can seamlessly update??? If TWC is too lazy to modify ONE LINE OF TEXT, it's really just pathetic.
I used the file linked here, thanks to Silverhawk, and had no problem - http://www.megaupload.com/?d=TCUGTUXT
Simply dragged/dropped the .xpi file into Firefox, restarted, and set my settings. Worked just fine.