Here are the time series plots of the statewide average temperature for February and winter (December-January-February) from 1895 to present (source: NOAA NCDC).
In the first plot, I have a red box around the temperature for 2014 and 2015. The only other time that we had a pair of extremely cold Februarys was 1978 and 1979. All the other cold Februarys were one-off events. According to NCDC, the statewide average temperature for February 2015 in Illinois was 19.5 degrees and the 9th coldest on record. Last February was nearly identical at 19.4 degrees.