Standardized Precipitation Index Table

East Climate Division

Illinois, Climate Division 05

Precipitation Data Table

Time Scale in Months (As of the end of Jan. 2026)
1 2 3 4 5 6 7 8 9 10 11 12 15 18 24 30 36 48 60 72
Accumulated Precipitation (in.) 0.97 2.68 4.39 6.05 7.24 9.37 14.36 18.35 21.32 24.82 28.2 28.67 35.71 41.9 64.35 84.22 101.27 135.98 177.38 214.08
Accumulated Precipitation Departure from Normal (in.) -1.04 -1.62 -2.52 -3.67 -5.69 -6.97 -5.83 -5.89 -6.94 -7.07 -6.57 -7.85 -7.8 -11.07 -8.81 -5.41 -8.53 -10.5 -5.75 -5.74
Accumulated Precipitation Percent of Average 48 62 64 62 56 57 71 76 75 78 81 78 82 79 88 94 92 93 97 97
Accumulated Precipitation Percentile (non-exceedance) 20.9 20.6 15.1 8.5 3.3 2 7.9 10.9 8 8.4 10.2 6.6 9.1 4.1 12 27.5 18.5 17.5 33.5 35.2
Standardized Precipitation Index -0.81 -0.82 -1.03 -1.37 -1.84 -2.06 -1.41 -1.23 -1.41 -1.38 -1.27 -1.5 -1.33 -1.74 -1.18 -0.6 -0.9 -0.93 -0.42 -0.38