Standardized Precipitation Index Table

Southwest Climate Division

Illinois, Climate Division 08

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.) 1.07 1.96 4.08 8.33 10.29 11.11 15.49 20.43 24.73 34.14 36.51 39.08 49.92 57.81 83.8 100.62 123.65 166.2 208.39 254.71
Accumulated Precipitation Departure from Normal (in.) -1.82 -4.03 -5.35 -4.2 -5.55 -8.18 -7.51 -6.6 -6.79 -1.67 -3.31 -3.36 -2.06 -4.04 -1.17 -3.77 -3.84 -3.81 -4.06 -0.24
Accumulated Precipitation Percent of Average 37 33 43 66 65 58 67 76 78 95 92 92 96 93 99 96 97 98 98 100
Accumulated Precipitation Percentile (non-exceedance) 13.1 1.9 2.5 12.3 8.3 2.8 5.8 11.3 13.3 42.4 33.4 33.7 42 33.8 47.1 38.7 39.4 41 41.4 50.4
Standardized Precipitation Index -1.12 -2.08 -1.96 -1.16 -1.39 -1.92 -1.58 -1.21 -1.11 -0.19 -0.43 -0.42 -0.2 -0.42 -0.07 -0.29 -0.27 -0.23 -0.22 0.01