And if you want to look at the calendar, Christmas is only 4 days into winter. Since it's not really the coldest time of year, it stands to reason that it's quite possible for areas that do get snow won't have it on Christmas.
In my region (Philly), it's likely we'll see some snow in December and even November, but with average highs still in the 40's it usually won't stick around.
In recent memory, I remember only 2 significant December snowfalls in my area:
A surprise early December storm where an inch or so was expected, and we wound up with 8 inches. This was also the only Eagles game that I ate the tickets, as I was called out to DOT to work the snow trucks. The game on TV was awesome to watch, but conditions for the fans at the game were miserable. This snow easily melted prior to Christmas though.
A heavy snowfall the Saturday before Christmas many years ago (when not a lot of shopping was done via internet), which shut everything down on one of the busiest shopping days of the season. A very intense effort to clear the roads and parking lots went well, and by Sunday people could resume their normal shopping. That year was definitely a white Christmas with plenty of snow still on the ground.