May in Illinois – Above Average Rainfall


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
That’s a spread of only 0.26 inches in four years!


The statewide average temperature for May was 62.1 degrees, 0.8 degrees below average. Temperatures ranged from a high of 95 degrees in Prairie City, Fisher, Little Red School House (Willow Springs), Princeville, and Trimble to a low of 24 in Elizabeth.
May 2011 rainfall in Illinois.
May 2011 rainfall in Illinois (click to enlarge).

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