Hello,
If you select multiple objects at once in the scenery editor list and then check "no snow" a checkbox appears in each object as it is supposed to. However, those objects still collect snow. I had a large collection of items inside a hangar with snow on them. Half of them I selected one by one until I realized I could use the multi select. The ones that I did one by one worked fine but the ones that I used multi select on still had snow on them. All of them had a checkmark in the check box for no snow however.
I had to go back and select each of these objects and clear the checkbox and then re-check no snow and they worked.