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.
The statewide average temperature for February was 18.6 degrees. That is 12.3 degrees below the 1981-2010 average and the 7th coldest February on record. By comparison, February 2014 was 9th coldest at 19.5 degrees.
Here are some amazing statistics for Chicago. February was tied with 1875 for the coldest on record, according to the Chicago National Weather Service. The average temperature for February was 14.6 degrees, 13.1 degrees below average. In addition, it was the 10th coldest month overall on record. February snowfall in Chicago was the third largest on record with 26.8 inches, 17.7 inches above average.
Snowfall for February in Illinois was widespread and well above average. Amounts of 15 to 20 inches were common in western and northern Illinois and 10 to 15 across central Illinois and parts of far southern Illinois. This was 8 to 12 inches above average in many locations. See maps below. Click to enlarge.
Some other February snowfall totals from around the state:
Chicago Midway AP: 28.3 inches
Rockford: 14.7 inches
Peoria: 12.8 inches
Quincy Lock and Dam: 11.2 inches
Springfield: 22.6 inches
Champaign-Urbana: 12.4 inches
Bloomington-Normal: 13.0 inches
Carbondale: 6.0 inches
The statewide average precipitation (rain plus the water content of snow) for February was 1.5 inches, 0.5 inches below average. Most of the state received 1 to 2 inches of precipitation, except for far southern Illinois which got 2 to 3 inches. See the second batch of maps for precipitation and precipitation departures from average.
While Illinois and the eastern half of the US freezes, temperatures in California and the West are well above average this month. Here is the map of temperature departures from average for the first 25 days of February. This pattern of extremes was the theme of 2014, diminished in December and January, only to return in February 2015. The temperature pattern is a result of a persistent ridge of high pressure in the West and a trough of low pressure in the East. This is discussed in some detail over at climate.gov
Goldilocks’ Porridge: there is a tiny white strip on the map from Montana, through the Plains states, and into Texas, where temperatures are within a degree of average – not too hot, not too cold, but just right.
February 2015 is on track to being one of the coldest February’s on record for Illinois. Data through February 24 puts the statewide average at 19.4° F. This is 11.5°F below average and slightly colder than last February’s 19.4°F. Before February, this was shaping up to be a mild winter with near to above-average temperatures (see graph to the left, click to enlarge).
At this point, February 2015 is ranked as the 8th coldest on record, edging out 2014 (see table below). The NWS forecasts show that temperatures for the rest of February will be 15 to 20 degrees below average. Therefore it is possible that it could move up the ranks. I will post more on this at the end of the month.