(Edit 2017: I do not wrap my hives all the way around any longer, just three sides so the bees can find their way home. I have not lost a hive to winter or spring thaw in many years.)
First snow yesterday. 20's today.
I did not wrap my hive last winter. It was a big colony with lots of stores and so I just chanced using hay bails on sides and back only with the front of the hive facing the sun. The bees withstood -20 F at night...it was a very hard winter and long and these were Italians. I kept the moisture out with pine needles in a super and a homasote board cut to fit for an inner cover on top of that.
This little hive you see in the picture swarmed in July and had little or no stores and they are in a very wooded yard, so I'm erring on the side of caution. Another concern I have is that the first time I wrapped a hive the bees came back from voiding flights and got lost under the wrap. I had it too high up to the upper exit and too low close to the lower entrance.