El Niño in Peru has been associated with heavy precipitation in the northern coast of Peru that is accompanied with a periodic warming of regional sea surface waters neighboring the coast. In general, the coast of Peru is very dry and rain falls only in the northern coast during El Niño events. In the Peruvian Andes seasonal rain prevails with heavier precipitation during the southern hemisphere summer months (December – March). Interannual precipitation variability has been observed in the Andean regions with excess rains in some years and rainfall deficits in other years. During the most recent El Niño events, this interannual precipitation variability has been tried to relate to El Niño events by a few researchers and particularly the media.

The purpose of this paper are: 1) to assess whether there are sifnificant relationship between anomalies in rainfall observed in the Peruvian Andes and El Niño events and 2) to investigate the relationship between anomalies in rainfall observed in the Peruvian Andes and sea surface temperature(SST) anomalies in the four geographical regions, Niño 1+2, Niño 3, Niño 3.4 and Niño 4 using linear lag correlation technique for the period 1950-2002. The assessment of these relationships is of particular interest for its application in long-range forecasting of rainfall and river flow in the Peruvian Andean region.

The analysis indicate that during years with El Niño events, three sifnificant subregional features are observed in the Andes, the north, central and south subregion. Precipitation tend to be higher than average in the northern subregion, neutral en the central subregion, and lower than average in the southern subregion.

It is found that the correlation indices between precipitation in the Peruvian Andes during the months of more intense precipitation and SST anomalies in the three regions Niño 1+2, Niño 3, and Niño 3.4 are negative and very weak, where as the correlation indices between precipitation in the central and southern subregion of the Andes and SST anomaly in the region Niño 4 are negative and moderate large, especially in February.

The analysis further indicate that the precipitation in the northern cost of Peru is highly correlated with SST anomaly in the Niño region 1+2, as several researchers have previously reported.