Standardized Precipitation Index Table

Snake Drainage Climate Division

Wyoming, Climate Division 02

Precipitation Data Table

Time Scale in Months (As of the end of May 2025)
1 2 3 4 5 6 7 8 9 10 11 12 15 18 24 30 36 48 60 72
Accumulated Precipitation (in.) 2.46 4.59 8.75 15.62 17.77 21.89 24.08 25.05 26.71 28.13 28.78 29.94 39.93 50.97 66.42 86.63 99.51 128.64 157.04 190.12
Accumulated Precipitation Departure from Normal (in.) -0.43 -1.14 -0.47 2.81 0.74 1.15 -0.04 -1.29 -1.41 -1.44 -2.06 -3.13 -2.36 -2.8 0.29 -0.14 0.4 -3.42 -8.04 -8.11
Accumulated Precipitation Percent of Average 85 80 95 122 104 106 100 95 95 95 93 91 94 95 100 100 100 97 95 96
Accumulated Precipitation Percentile (non-exceedance) 41.6 24.9 45.1 84.4 60.7 63 52.4 42.2 41.4 41 36.3 29.1 36.2 35 53.1 50.8 52.9 39.9 28.3 29.5
Standardized Precipitation Index -0.21 -0.68 -0.12 1.01 0.27 0.33 0.06 -0.2 -0.22 -0.23 -0.35 -0.55 -0.35 -0.38 0.08 0.02 0.07 -0.25 -0.57 -0.54