After the first seven days of December, it's going to be tough to whittle away a six degree above average temperature departure to get to average by month's end. The next 24 days would require temperatures of at least 2.2 degrees below average in order for the month to finish at or below normal.
Given the upper level pattern between now and Christmas, normal or below is pretty unlikely for the month of December.
That isn't to say we won't have colder air from time to time -- we will starting on Tuesday and continuing through Thursday, and probably will have colder shots of air later in the month. However, the pattern doesn't support locked-in cold for us in the Eastern US. Europe is another story -- it's pretty cold there and looks like it will be that way for much of the next week; however, our weather will be seasonally crisp for the middle and latter parts of the week before we warm back up late next week.
Looking at the European ensemble modeling -- the Euro has an ensemble suite as well of 50 or so different variations -- the ensemble mean is showing another warm shot for next weekend and into the week before Christmas, probably ending on the 19th or 20th with another storm system passing through.
If you want "cold" -- it might be a while to get it on a sustained basis. Even around Christmas the pattern looks cool but not terribly cold, with more persistent cold setting up shop in Alaska and Yukon in about a week's time and holding firm through the days leading up to Christmas (see map below).
December will end up as a mild month, perhaps by a factor of three or four degrees by month's end. We talked about how years where December ended up not much colder than November and this year could be one of those years where the temperature trend between months is only a couple of degrees colder unlike the normal drop of ten or so degrees between November and December.