Northern Rockies and Plains Climate Region, Precipitation, 24-Month Period Ending in March Inches 1901-1905 -99 189703 39.43 2.16 189803 39.83 2.56 189903 36.28 -0.99 190003 36.08 -1.19 190103 35.58 -1.69 190203 37.61 0.34 190303 37.55 0.28 190403 38.93 1.66 190503 36.67 -0.60