A few tidbits about this past winter...
Chicago and Rockford Winter 2011-2012Note how 2011-2012 is tied for 6th place with 1931-1932 with 50 40 degree days.  
EVERY winter above this winter on this list is from the 
1800s!  Of the ten winters listed on that "Chicago: 40 Degree Days" graphic, only 
THREE have occurred within the past 65 years.   

I know the "official" recording station (currently at O'Hare Airport) has been moved at least once in the past century, but that's no excuse.  Let's face facts here: winters like this past one (without prolonged Arctic cold) are nothing new!