The precipitations of a region (annual accumulation as well as its distribution), are the climatic variable with greatest impact on agricultural production. In recent years, interest have grown among farmers about the El Niño- Southern Oscillation (ENSO). However, although there is a usual believe that: “during the warm phase, El Niño, rainfalls are higher than average”, this expression can results ambiguous, and even false, if not contextualized in a spatio-temporal context. In this paper, rainfalls were characterized for the locations Paraná (PAR) and Lucas González (LG), in relation with the Oceanic Niño Index (ONI, quarterly index published monthly by the Climate Prediction Center –CPC– of the National Oceanic and Atmospheric Administration –NOAA–). This index showed a significant... positive correlation coefficient (r between 0.5 and 0.65) with the amount of precipitation in the springsummer quarters of both locations, even when considering the ONI from several previous months, hence making it an interesting precipitation predictor. Therefore, for the analyzed locations and the region in which they are located, the results obtained in this paper provide a tool that farmers could use for management decisions that will enable them to reduce risks by facing each year with greater certainty.