Once in a blue moon all the widgets might disappear don't know why, I find when changing the appearence of the weather widget too much may make them disappear. You can also use Foreca Weather as well.
/usr/share/applications/hildon-home/calendar-home-applet.desktop /usr/share/applications/hildon-home/omweather-home.desktop /usr/share/applications/hildon-home/google-search-widget.desktop /usr/share/applications/hildon-home/homeosso_rss_feed_reader.desktop /usr/share/applications/hildon-home/location-home-applet.desktop /usr/share/applications/hildon-home/mediaplayerhomeapplet.desktop /usr/share/applications/hildon-home/ovi-promotion-widget.desktop /usr/share/applications/hildon-home/tutorial-home.desktop /usr/share/applications/hildon-home/conversations-inbox-widget.desktop /usr/share/applications/hildon-home/facebook.desktop /usr/share/applications/hildon-home/foreca-weather-applet.desktop /usr/share/applications/hildon-home/omweather-home.desktop /usr/share/applications/hildon-home/personal-ip-address.desktop /usr/share/applications/hildon-home/personal-photo-frame.desktop /usr/share/applications/hildon-home/simple-fmtx-widget.desktop /usr/share/applications/hildon-home/sleeper.desktop