It should come as no surprise that the May 2011 statewide average rainfall was 5.60 inches, and 1.34 inches above the 1971-2000 average. In the first half of May, the rainfall distribution was lopsided with southern Illinois getting 3-5 inches of rain while much of the rest of the state had less than 2 inches. But the rest of the state caught up in the second half of the month.
For May, the two sites with the heaviest rainfall totals in the NWS cooperative observer network were near the Quad Cities: Woodhull with 9.92 inches and Altona with 9.28 inches. From the CoCoRaHS network, the two sites with the heaviest rainfall totals were on opposite ends of the state: Anna with 10.04 inches and Algonquin with 9.12 inches.
Here is an amazing thing about the statewide May rainfall – they are almost the same in the last four years:
- 2011 – 5.60 inches
- 2010 – 5.59 inches
- 2009 – 5.65 inches
- 2008 – 5.39 inches