It's Back Rated 4 out of 5 stars
Thanks to SilverHawk and his tweaks a working version of this add-on is available again. Thumbs down to The Weather Channel for not keeping this add-on up to date. Don't download from this site (the add-on won't work). Following is the link and download instructions to get the working version (note: you'll have to wait 45 seconds to start the download).
To install it:
1) Download the archive from the link above.
2) Remove the existing addon from Firefox and restart Firefox.
3) Click on File->Open and browse to where you downloaded it to.
4) Select the archive and let it install.