The statewide average temperature for April 2012 was 54.1 degrees, based on available data. The statewide average temperature for March was 55.0 degrees, based on the latest numbers from NOAA. That means that April was almost a degree cooler than March. What makes this even more impressive was that the April temperatures are still 2.4 degrees above normal!
By the way, the statewide normal monthly temperature is 40.7 degrees for March and 51.7 degrees for April, an eleven degree rise.
How rare is it for April to be colder than March? In the statewide records that extend back to 1895, it happened only in 1907 when the March temperature was 47.0 degrees and the April temperature was 43.2 degrees. In all the other cases between 1895 to 2011, April was always warmer.
The highest temperature reported in the state for April was 92 degrees at Kaskaskia on April 2 and at Jacksonville and Pana on April 3. The coldest temperature reported was 23 degrees at Jerseyville on April 17.
The statewide average precipitation was 3.32 inches. That is about 0.5 inches below normal. The rainfall over the weekend was fairly widespread and helped much of the state. In general, the heaviest rains of 5 inches or more fell east of St. Louis. Meanwhile, rainfall amounts of 2 inches or less fell in far southern Illinois, far northwestern Illinois, and a large swath between Peoria and Kankakee. Those areas were 1 to 3 inches below normal for the month (second map).
The highest monthly rainfall total reported in Illinois for April was a CoCoRaHS observer near Belleville (IL-SC-3) with 8.64 inches. Some of the lowest monthly rainfall totals in the state were in Kankakee and Will Counties. For example, Grant Park (IL-KK-19) in Kankakee County reported all 30 days and only received 0.83 inches for the month.