Pat (Palo) is correct. With ubuntu 12.02 and its derivitaves, with xfce-panel 4.8, the indicator does not work. Version is 8.2 or below even with updates. You have to update to version 8.3 or above of the indicator, which requires XFCE 4.10 or above panel (which I discourage because many things on it do not work "properly" such as not showing all applications in the menu, for example.) It's just not worth it, unless you're doing a distribution upgrade, in which case I'd wait for the next LTS which is due in April 2014 (ubuntu 14.04 and derivatives,) which will use XFCE panel 4.11 or 4.12.
I tried Xubuntu 12.10, 13.04, and 13.10, and the indicator worked fine, but the problem was, nothing else worked correctly!
The version of the panel that works, as I said, requires an entire XFCE update, or you'll run into problems. They have not backported the new version to the older XFCE, I'm not sure if it's just the way it's coded to require features of the newer panel or what. The dev PPA where you can get it does not inform you of this, and think about it, it's a devolopment version, so you'll not want to try all the "experimental" stuff on it. Versioning for some reason is very important here.
I haven't checked, but other window manager systems such as KDE may have something but again, you'll be changing your whole system for one small indicator.
I'm back on 12.04, happy, and I just installed the accuweather indicator IN MY BROWSER instead. I figure I pretty much have the browser open if I'm online anyway, so that works fine. (In Firefox and the status bar is hidden you'll get NOTHING, install status4evar and set it to show the bottom panel, and this will work.) I couldn't get any of them to work in the latest (31) Chromium/Chrome, as it does not, by default, have widgets or non-static indicators anymore, and obviously no status bar. I think the whole idea of applets/system tray icons is going by the wayside! (Chrome does have extensions where you can set new tab to show the information, but that's inconvenient.)