EXPLAINED: Why India witnessed early’ onset of South-West monsoon this year?

The India Meteorological Department (IMD) has predicted the onset of the southwest monsoon in Delhi on June 24, three days ahead of the usual date of June 27. Similarly, IMD has predicted the monsoon in Kerala on May 27, but it has arrived early on Saturday, May 24, eight days ahead of its usual onset date of June 1. Last time, India witnessed the early arrival of monsoon in 2009.

The early monsoon has not only been witnessed in Kerala, but it has also advanced to the Lakshadweep area, the south Arabian Sea, parts of the west-central and east-central Arabian Sea, and some parts of Karnataka and Maharashtra. It has also covered the remaining areas of the Maldives and Comorin, several parts of Tamil Nadu, and the southwest and east-central Bay of Bengal, along with parts of Mizoram and the north Bay of Bengal.

So, did you wonder why most parts of India are experiencing the early onset of the South-West monsoon in 2025? In addition, Delhi NCR also remained free of heatwaves due to frequent pre-monsoon showers in May and June.

Why early South West monsoon in India this year?

Basically, the early onset of monsoon in India this year is driven by favourable atmospheric and oceanic conditions, as a low-pressure area developed along the Arabian Sea with a trough line extending across Vidarbha. This low pressure prompted the inflow of moisture and atmospheric convection, which accelerated the advancement of the monsoon over the Indian subcontinent.

A key indicator of the monsoon’s rapid advancement was its early arrival over the south Andaman Sea and nearby regions on May 13, significantly earlier than the usual date of May 21. This early onset set the stage for its quick progress toward Kerala. Contributing to this development were neutral El Niño–Southern Oscillation (ENSO) conditions, which generally favour a normal or stronger monsoon, unlike El Niño phases that tend to weaken rainfall across India. Additionally, lower snow cover in the Himalayan region, historically linked to stronger monsoon patterns, may have also played a role.

What is El Niño

El Nino is a natural phenomenon which refers to the large-scale ocean-atmosphere climate interaction which links to periodic warming in the temperatures of the sea surface across the central and east-central Equatorial Pacific. This phenomenon is directly linked to high pressure in the western Pacific, which adversely impacts the Indian monsoons that bring a catastrophic impact to agriculture in India.

Due to El Niño, the cold surface water off the Peruvian coast gets warm. When the water is warm, there is a reversal of the normal trade winds, or they get lost. Later, the moisture-laden winds are directed towards the coast of Peru from the western Pacific (the region near northern Australia and South East Asia). As a result, heavy rains occurred in Peru during the El Niño years, ceasing the normal monsoon rains in the Indian subcontinent. Hence, when there is a larger temperature and pressure difference, the larger the rainfall shortage in India.

Which key sectors benefit from the early monsoon?

The early monsoon supports crucial sectors like agriculture, fisheries, and livestock, which heavily depend on seasonal rains, which play key roles in financially benefiting the people working under these sectors. A strong monsoon not only boosts preparedness for extreme weather and climate risks but also highlights the value of government spending on forecasting and weather-monitoring systems.

Major efforts such as the Monsoon Mission and high-performance computing-based weather prediction models have, in recent years, enhanced resource planning, improved crop productivity, and helped minimise weather-related damages.