The three snowiest Decembers on record in Milwaukee have all occurred in my lifetime, all in the last ten years ... 2000, 2007 and 2008.
Everyone of these was roughly an average Milwaukee winter's worth of snow.
Oh my aching back!
John in Wauwatosa
P.S. Something like 10 or more of the warmest years on record have occurred in the last 15 to 20 years. The official weather records here go back to aprox 1870 as Increase Lapham, a prominent Wisconsin scientist was a founder of the US Weather Bureau, now part of NOAA.

Talk about Snow Jobs
Perhaps not a record for December in Milwaukee but one of the hardest combined snowfalls in a like period of time occurred between December 31st and January 24th of ‘78/’79 with 37.8 inches,with drifting adding another six feet. These same storms paralyzed Chicago and resulted in Jayne Byrne ousting Mayor Michael Bilandic, after this major snow belt city could not clear the streets fouling traffic for weeks. One reason I remember, was work entailed to clear out the alleyway at 13th and Juneau as I tried to free my car, luckily there were only two other yards between me and 13th street.
For our friend in Norway, or those of you on the US West Coast, these are snowfalls without the benefit of warm moisture being driven up over coastal mountains to create massive snowfalls, in the terms of six feet in a day. Normal weather patterns have West and Northwest winds bringing storms from over the planes, with the nearest water over a thousand miles away (2000 from the west, or 1000 from the south)The normal heavy snow fall requires a high to the northwest and a low working its way from Texas toward Lake Michigan, helped by a dip in the Jet Stream. The rare winter storms coming from the east of course will pick up moisture from Lake Michigan, but these will only affect inland about 90 miles.