KAMasud, are you sure it was 10 C ? You wouldn't have any snow for very long at that temp. It's equal to 50 F.
-10 C or 10 F would allow for the snow. Good snow cover allows many plants to be wintered over in ground that wouldn't otherwise live through the winter. I live in zone 5b yet have plants rated for zone 6 & 7 survive because in a typical winter ( this last certainly wasn't) we get as much as 5 - 6 feet of snow with outside temps of -20 C
