Precipitation constitutes an important part of the hydrologic cycle, since it produces the planet’s renewable water resources. In semi-arid regions, like Ensenada, Baja California, Mexico, where the rainfall throughout the year is generally scarce, it is of great importance to be able to predict the precipitation and make necessary arrangements to prepare for draughts or floods. The main objective of this thesis is the rainfall characterization of the catchment area of Ensenada, Baja California, Mexico. In order to do that, 60 years of data from seventeen meteorological stations was studied, previous restoration by means of multiple regression method and NIPALS algorithm. The restoration was followed by obtaining extreme and mean climate for each station. In order to establish a trend existence, that is, if the rainfall has experimented a decrease or an increase through the years, the Mann-Kendall trend test was applied. Following that, cross-correlation technique was applied so as to establish a correlation existing between the mean and maximum precipitation values and the North Pacific climate index and the El Niño index. The results of this thesis include the Weibull distribution parameters for extreme and mean climates for the seventeen meteorological stations, tabulated and graphical Mann-Kendall trend test results for mean and maximum precipitation values for the seventeen stations and graphical results for the correlation between the climate indexes and mean and maximum precipitation values. These results provide an insight into the rainfall characterization of the area may be used as a management tool for decision makers and good water use policy.