The year 2012 will long be remembered for the drought and the exceptionally warm temperatures. While the data for December is still preliminary, it was the second warmest and tenth driest year on record for Illinois.
The statewide average temperature for 2012 was 55.5 degrees, 3.3 degrees above normal and the second warmest year on record for Illinois. The warmest year was 1921 with 55.6 degrees. Temperatures were much warmer than normal in January-May, July, and December (figure below). For some places in Illinois it was the warmest year on record, including Chicago and Rockford (see story here).
The statewide average precipitation for 2012 was 30.37 inches. That was 9.83 inches below normal and the 10th driest year on record in Illinois. The normal annual precipitation in Illinois is 40.20 inches. Precipitation was much drier than normal in May-July and November (figure below). Here is how 2012 compared with other dry years:
- 1901 – 26.34″
- 1930 – 27.88″
- 1963 – 28.00″
- 1953 – 28.05″
- 1914 – 28.58″
- 1976 – 28.84
- 1940 – 29.33″
- 1988 – 29.71″
- 1936 – 30.24″
- 2012 – 30.37″
The map of the precipitation departures from normal across the state (below), as of December 31, 2012, shows large areas of the state with deficits in the range of 8 to 16 inches below normal (the darker tan and bright red colors) for 2012.
Unfortunately, winter is our driest time of year in Illinois. The normal precipitation for January and February is 2.11 and 2.12 inches, respectively. Even March is not much wetter at 2.98 inches. That adds up to 7.21 inches for those three months combined. It would take something close to record precipitation in January (6.92 inches), February (4.46 inches), and March (7.53 inches), for a total of 18.91 inches, to erase the deficits accumulated in 2012.
The statewide average precipitation for December 2012 was 2.34 inches, just 0.4 inches below normal.
The statewide average temperature for December 2012 was 35.8 degrees, 5.9 degrees above normal and the 13th warmest December on record. The warmest December on record was 1923 with 39.7 degrees.