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Droughts are a regional and recurrent natural phenomenon, which is governed by local climatic parameters. Since the annual average precipitation is the fundamental quantity defining the climate, in this study it is used for the classification and the identification of the occurrence of meteorological droughts. Thirty-two complete annual rainfall records were processed from the state of San Luis Potosi, Mexico, whose amplitudes ranged from 45 to 55 years. These annual series define four climates, and an extremely simple model to detect and estimate the severity of droughts was applied to them. Two representative values of each climate were obtained: drought occurrence percentage (%0) and average intensity (AI). In the arid climate, the representative %0 was 26.9, with a 0.446 AI. For the semiarid climate the %0 decreased to 22.2 with an AI of 0.379. In the subhumid climate, both indicators fell, to 18.5 and 0.336, respectively. Lastly, in the humid climate the %0 decreased to 16.4, but the AI increased slightly to 0.344. The analysis of the occurrences of droughts in the years analyzed enables drawing conclusions about their temporal distribution, yearly and spatially, within the state of San Luis Potosi, Mexico. Conducting these analyses in other regions of the country is recommended, due to the importance of those estimations in order to understand the behavior of meteorological droughts in a region or state.