It looks like it's averaged a bit warmer in Buffalo than here, but still it's been very mild since the 3rd week of December. Neither December or January will show up in the all time warm lists because of the cooler start to December in what looks like a cold end to January. But I'm sure if you take an intra month 30 day period, it's up there. But i always believe the heart of Winter is mid January to mid February, I never consider mid December to mid January the "heart" of Winter. As for rarity, February 2015 is in a very elite minority group (much like march 2012), I have to say this mild stretch does not come close to it, at least here.