Periodic rise in temperature of surface water of the Pacific Ocean near the Equator causing widespread changes in climate and weather petterns in large areas in both the Hemispheres. These changes cause draught, floods, excessive rain-fall, hurricanes of greater intensity, atmosheric pressure wind stream changes leading to extremes of hot or cold conditions. El Nino, little child in Spanish ( a reference to Christ Child ). It was first noted off the shores of Peru by the fishermen in late December, thus the name.

El Nio-Southern Oscillation (ENSO; commonly referred to as simply El Nio) is a global coupled ocean-atmosphere phenomenon.