Standardized Precipitation Index Table

Northwest Climate Division

Illinois, Climate Division 01

Precipitation Data Table

Time Scale in Months (As of the end of Jul. 2026)
1 2 3 4 5 6 7 8 9 10 11 12 15 18 24 30 36 48 60 72
Accumulated Precipitation (in.) 2.57 9.7 11.1 18.15 21.24 21.44 22.18 23.8 25.74 27.61 28.3 31.61 46.81 53 63.38 87.9 103.86 138.64 171.54 205.91
Accumulated Precipitation Departure from Normal (in.) -1.34 1.48 -1.11 2.56 3.2 2 1.21 0.99 0.71 -0.09 -3.03 -3.48 -0.5 -1.52 -6.84 -1.73 -1.54 -1.93 -4.22 -5.1
Accumulated Precipitation Percent of Average 66 118 91 116 118 110 106 104 103 100 90 90 99 97 90 98 99 99 98 98
Accumulated Precipitation Percentile (non-exceedance) 24.2 73.7 39.5 76.6 79.6 70.6 63.5 61.2 58.4 51.6 30.4 28.2 49 43.6 20.8 44.3 45.4 44.9 39.1 37.9
Standardized Precipitation Index -0.7 0.63 -0.26 0.73 0.83 0.54 0.35 0.28 0.21 0.04 -0.51 -0.58 -0.02 -0.16 -0.81 -0.14 -0.11 -0.13 -0.28 -0.31