This report is the culmination of a cooperative project with the centro internacional para la investigación del fenomeno de “el niño” (ciifen) in order to satisfy or, putting in other words, solve ciifen’s problem on developing the first drought tool for their impact-based forecast and warning services (ifws) initiative for agriculture areas and population density. the problem was defined as follows: “the current ciifen’s drought tool, the standardized precipitation index (spi), has a spatial resolution of 1º by 1º that does not provide detail spatial information to develop an ifws drought tools for agriculture areas and population density”. to solve this problem was necessary a literally review to find precipitation sources (data) with a better spatial resolution than the one that ciifen currently has, as well a review to understand the theory behind the impact-based forecast and warning services. the results of this review were: finding the precipitation climate hazards