Standardized Precipitation Index Table

East Climate Division

Illinois, Climate Division 05

Precipitation Data Table

Time Scale in Months (As of the end of Aug. 2020)
1 2 3 4 5 6 7 8 9 10 11 12 15 18 24 30 36 48 60 72
Accumulated Precipitation (in.) 1.56 6.24 10.55 15.82 20.44 23.5 25.53 29.61 31.16 32.77 37.3 42.9 52.38 67.69 86.03 107.37 123.05 162.13 208.61 251.52
Accumulated Precipitation Departure from Normal (in.) -1.84 -0.97 -0.73 0.5 1.48 1.68 1.96 4.02 3.2 2.17 3.91 6.25 4.44 9.24 12.8 12.36 13.26 15.8 25.73 32.16
Accumulated Precipitation Percent of Average 46 87 94 103 108 108 108 116 111 107 112 117 109 116 117 113 112 111 114 115
Accumulated Precipitation Percentile (non-exceedance) 6.1 36.5 44.7 58.4 66.4 67.6 68.9 81.6 76.3 68.8 78.8 87.1 75.6 90.9 93.9 91.2 90.5 91.1 97.2 98.4
Standardized Precipitation Index -1.55 -0.35 -0.13 0.21 0.42 0.46 0.49 0.9 0.72 0.49 0.8 1.13 0.69 1.34 1.54 1.36 1.31 1.35 1.91 2.14