How a Pacific ocean pattern changes India's monsoon winds

How can warm water in the middle of the Pacific Ocean change the monsoon over India? The link runs through the air.

Step 1: the Pacific. During El Niño, the trade winds weaken and warm water spreads east across the tropical Pacific.

Step 2: the air. Rising air, clouds and rain move east with the warm water. The large-scale circulation, including the Walker circulation described by Sir Gilbert Walker of India's weather service, is disturbed (IMD Nagpur).

Step 3: moisture. IMD says El Niño "generally suppresses the Indian summer monsoon by weakening the large-scale atmospheric circulation responsible for transporting moisture toward the Indian subcontinent."

Step 4: on the ground. Typical effects listed by IMD are below-normal rain, more dry spells, higher temperatures and heatwaves, lower reservoir inflows and lower farm output. Many major drought years, including 1982, 1987, 2002, 2009 and 2015, came with El Niño.

But it is not automatic. Other drivers matter, especially the Indian Ocean Dipole. A positive IOD can partly offset El Niño's drying. In 1997, a strong El Niño year, India's monsoon was normal (IMD).

This year. India's June–September 2026 rain was 87% of the long-period average, in the "deficient" category (IMD, 30 September 2026).

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