According to Dr Raghu Murtugudde, Emeritus Professor at the University of Maryland and former professor at IIT Bombay, moisture from both the Arabian Sea and the Bay of Bengal has been strengthening the monsoon system. A low-pressure area developing over the Bay of Bengal further intensified the weather conditions, leading to widespread heavy rainfall.
As moisture-laden winds moved towards the west coast, the Western Ghats forced these winds to rise, resulting in intense rainfall across Mumbai and coastal Maharashtra. The combination of multiple weather factors created conditions favourable for exceptionally heavy precipitation in the region.
The recent rainfall pattern also reflects a long-term climate trend. Mumbai’s average annual rainfall increased from 2,325.8 mm during 1981–2000 to 2,672.7 mm between 2001 and 2024, marking an increase of nearly 15 per cent.
Traditionally, El Niño has been associated with weaker monsoon conditions in India. The climate phenomenon refers to unusually warm sea surface temperatures in the central and eastern Pacific Ocean, which often delay the southwest monsoon and reduce the number of rainy days across the country.
This year, Mumbai’s monsoon arrival was delayed by nearly two weeks, while Gujarat, Madhya Pradesh, Chhattisgarh and Maharashtra also experienced delayed onset. However, the Prime Minister’s Office, citing India Meteorological Department officials, stated that an El Niño year does not always result in below-normal rainfall.
Rainfall across India improved significantly during the first week of July, reducing the national monsoon deficit to 12 per cent. A weak-to-moderate El Niño condition is expected to continue through July and August.
Scientists have stated that climate change is altering not only the quantity of rainfall but also its pattern. A warmer atmosphere and rapidly warming oceans allow the air to retain greater amounts of moisture. As a result, rainfall is increasingly occurring in short-duration, high-intensity bursts rather than being distributed evenly over several days.
These intense rainfall events often put pressure on drainage systems and increase the risk of flash floods in urban areas.
Dr K. J. Ramesh, former Director General of the India Meteorological Department, told The Indian Express that although El Niño years generally witness fewer rainy days, “the character of the monsoon has changed permanently due to global warming,” with rainfall now occurring in short-duration, high-intensity spells.
Experts have emphasised that El Niño can no longer be examined separately from the impact of climate change. According to Dr Murtugudde, global warming over West Asia, changing Arabian Sea wind patterns and rising ocean temperatures are increasingly interacting with El Niño, making monsoon behaviour more complex than in previous decades.
While El Niño continues to influence the timing of monsoon arrival, climate change is increasingly determining the intensity of rainfall once weather systems become active.
Meteorologists have stated that a delayed monsoon onset does not prevent episodes of extreme rainfall later in the season. Once favourable atmospheric conditions develop, heavy rainfall can occur even during an El Niño year.
The current rainfall spell appears to be weakening, with both Colaba and Santacruz recording below three-digit rainfall totals for the first time in five days. However, the India Meteorological Department has stated that monsoon conditions remain active, while its latest forecast indicates lighter rainfall over Mumbai and neighbouring Thane during the coming week.
Scientists have highlighted that while El Niño shapes large-scale climate patterns, local weather systems ultimately determine the location and intensity of rainfall. During the latest spell, simultaneous moisture inflow from the Arabian Sea and Bay of Bengal, a developing low-pressure system over the Bay of Bengal, and the lifting effect of the Western Ghats combined to produce exceptionally heavy rainfall over Mumbai.
The latest rainfall episode has reinforced a broader scientific understanding that India’s monsoon behaviour can no longer be assessed through El Niño alone. Increasing interactions between global warming, ocean changes and regional weather systems are reshaping the nature of extreme rainfall events across the country.
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