at home are you on a airave? also you can add citys the database by using a editor. if your on a airave at home nothing you can do about it except update via wifi. what i did was make my city a second selection on weather tab. then on main press clock and select or add your citys time zone as main. so its the displayed weather bypassing the location weather on main screen.
here is a link to the editor on xda.
Manila 2.1 and 2.5 JVH3 Weather City Editor - Version 3.5 | updated 3/15/2010 - xda-developers