El Niño (meaning “the little boy” in Spanish) is a climate pattern that describes the unusual warming of surface waters in the eastern Pacific Ocean, which occurs irregularly in 2 – 7 years

Formation

• Trade winds weaken or reverse, reducing the westward push of warm water.
• Warm water shifts eastward toward the Americas.
• Upwelling of cold, nutrient-rich water off South America weakens.
• Walker circulation collapses/weakens, altering global weather patterns.

Impacts

• El Niño weakens the southwest monsoon, resulting in below-normal monsoon rainfall, and the onset of the southwest monsoon may be delayed. 
  • Uneven distribution of rainfall and cause drought like situation.
• Poor monsoons fail to adequately replenish major reservoirs and underground aquifers, causing acute water stress for irrigation and drinking in the subsequent months.
• Deficient rainfall severely impacts Kharif (summer-sown) crops like rice, pulses, and sugarcane, leading to delayed sowing and lower crop yields.
• Lower agricultural output drives food inflation, reduces rural income and consumer demand, and strains government fiscal management through drought-relief spending.

Source: The Hindu