The scrolling animation is still shown if only one value (e.g. temperature) is chosen. A plugin restart resolves this behaviour but this should be applied immediately. How to reproduce: Just disable all except one value.
Fixed in http://git.xfce.org/panel-plugins/xfce4-weather-plugin/commit/?id=e52c04b5c229fc61618a422190e1a9d69124e56f Thanks for reporting.