Current weather plugin doesn't work at all with 4.7 panel.
First, it lacks linking against libxfcegui4 (since xfce4-panel switched to libxfce4ui), but above all it lacks RGBA support, and it segfaults as soon as it's added to the panel.
Nick Schermer drafted a patch against an old weather plugin version, you can find it at http://foo-projects.org/~nick/plugin-migration/xfce4-weather-plugin.patch but it doesn't apply anymore.
Created attachment 3428
Fixed Nick's patch.
This patch also closes bug 7189.
*** Bug 7189 has been marked as a duplicate of this bug. ***
Applied patch without the icon handling changes that were somewhat wrong, see bug 7209.