Good question...I have been wondering this myself, about when I will take the plunge and ditch socks. Lisap said she doubts that there is snow on the ground when it is 60F, but it is 60F here today, and there are still lots of snow piles everywhere, ha ha. I toyed with the idea of wearing pumps without socks today, but it just seemed wrong. I think I will let my fashion sense rather than the temperature tell me when to ditch the socks.
I have been wearing closed-toe booties with nude knee-hi's, though. I'll probably just continue that for the time being, because I don't get much of a chance to wear high-heeled booties. The weather isn't mildly cold for long--usually it's either too hot or else too icy for these types of booties.