Select "REGIONS" from the same window you use to place 'Doodads.' Make sure that the "new region" box is selected (green) and then drag your mouse on the map where you want to make snow. Then right click the new region listed in the other window and select EDIT REGION. A new window should apear. At the bottom you'll see a drop box with different weather effects. Choose the one with snow and you'll have snow flakes on no time.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.