After setting the Measurement Units to "Imperial" in the Properties dialog, the displayed units are still metric. ~/.config/xfce4/panel/weather-21.rc does contain the line "celcius=false". I'm not fluent enough in C to see why this isn't working. Please accept my apologies if this is a duplicate bug.
Created attachment 4256 Added support for imperial units (temperature only) Existing version ignores the unit setting and uses units provided by the meteo service instead. This patch forces local units and converts the remote units (currently temperature only) if necessary. Technical data: The function get_data takes additional argument "unit" to check the local settings. It returns a newly allocated string (because a conversion might be necessary) so all uses of this function have to explicitly g_free the result now.
Created attachment 4257 Added support for imperial units (temperature only) Fixes a memory leak in the get_units function (CHK_NULL macro now allocates memory).
Support for unit conversion/display is now in git master (http://git.xfce.org/panel-plugins/xfce4-weather-plugin). Thanks for reporting and the patch.