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Sustainable livestock production is dependent on reliable forage resources that maintain animal health and reproductive fecundity. Temporal and spatial variation in forage production in most range systems is closely linked to the timing and amount of precipitation.  Livestock producers often make grazing management decisions based on their knowledge of past or average forage production levels with little certainty that sufficient precipitation will fall in time to produce what is anticipated. The cumulative effects of inaccurate grazing management decisions are loss in soil fertility, increased rates of soil erosion, and establishment of weeds.  Research has linked global precipitation patterns with the occurrence of grass, shrub, and forested lands and provided regression functions relating Aboveground Net Primary Production (ANPP) with Mean Annual Precipitation (MAP). These tools are sometimes used to understand the impacts of drought on forage production for a given land unit. However, these globally derived functions are of limited use for making management decisions as they cannot account for temporal and spatial precipitation patterns that also influence forage production.  Thus, development of a rainfall and forage production index that accounts for temporal and spatial patterns in precipitation inherent to a given locale will greatly improve the management decision process. The purpose of this study was to quantify the relationship between local precipitation patterns with forage production in major rangeland ecosystems commonly grazed in Hawaii. Fifteen weather station and forage production exclosures were established across the state. Weather data were recorded hourly and forage production estimates were collected quarterly from all exclosures for three years. Regression analyses were used to develop the Hawaii Rainfall and Forage Production Index that will be useful for forecasting forage production and suitable stocking rates, drought planning and mitigation, development of prescribed grazing standards, establish soil erosion mitigation standards, and planning range improvement projects.