So how cold have the last couple of winters been?: One measure looking at the percent of the Great Lakes that are frozen over
The percent of the Great Lakes that have frozen over provides one measure of how consistently cold the winter has been. The Great Lakes also cover a very large area of North America so colder temperatures in just Chicago won't get you into the 80 or 90 percent range of the lakes that are frozen over. The NOAA data used in the top graph only go back to 2009 (which is very similar to 2010).
Currently, the percent of the Great Lakes that are frozen over is the second highest this decade. The new blast of arctic air headed down this week will surely increase the percent of the Great Lakes frozen above 80 percent and is likely to put the percent frozen over the level in 2014.