Abstract In this study El Nino effects on rainfall in Iran is evaluated. Annual rainfall data of the selected rain gauging stations for the years when El Nino phenomenon has taken place (1973-2012), have been picked up. Next, annual rainfall of the years with and without El Nino phenomenon were compared and then analyzed (correlation is significant at the 0.01 level). Finally, percentage-frequency of the rainfalls influenced by warm Enso condition was obtained. Regarding that El Nino has different affect on rainfall under different regions of the world, the results approved that El Nino, increases rainfall across Iran plateau as annual rainfall is increased from south to north. While less increasing of rainfall is seen for coastal area. Results showed that El Nino causes increasing of annual rainfall in Iran. Keywords: Iran; El Nino, Rainfall; Warm ENSO; Wet
