The scarce information that is counted and its importance in hydrological studies helps us to understand, simulate, and predict the events associated with the behavior of water. I think it is necessary to check the gridded data PISCOpm V.2.1 monthly rainfall with the observations in our Tumbes basin. For this, a comparative study was carried out between the observed and estimated values, concerning the weather station, elevation, seasonality of the year, and climatic region. Indicators such as the Coefficient of Determination(R2), Nash-Sutcliffe Efficiency Index (NS), and Percentage Statistical Bias (PBIAS%) were considered. At the monthly level, good correlation results were obtained, with values greater than 0,61, in the Nash - Sutcliffe efficiency index values greater than 0,60 and a minimum variation in the Percentage Statistical Bias. Regarding the elevation of the basin, data were obtained with a minimum adjustment in all the indicators. For the seasonal arrangement, summer presents the best average fit, followed by fall and spring. Winter presents a very good adjustment for 4 out of 9. Finally, of the 3 climatic regions, the D(i)A' region presents the best adjustment in the 3 indicators. It was possible to verify the adjustment of the data, having different results according to the evaluated criterion. This supports the use of observed data and its usefulness for studies in the Tumbes basin such as floods, droughts, hydrological and hydraulic modeling, completion of missing data, etc. Based on the results, studies of water availability, analysis of extreme events, etc. can be carried out.