A new study has found that El Niño events, long known to reduce India’s overall summer monsoon rainfall, also make extreme daily rainfall more intense in many parts of the country. The research, published in Science on September 18, 2025, examined rainfall records from 1901 to 2020 and revealed a surprising pattern.
The study was led by Spencer A. Hill, assistant professor at City College of New York, with collaborators from Columbia University and other institutions. Using more than a century of daily rainfall data from the India Meteorological Department, the team tracked how El Niño years influenced rainfall extremes across the subcontinent.
“Our key finding is that you tend to get more days with extreme amounts of rainfall within India, not less, in El Niño summers,” Hill said. “This finding was unexpected, because it has been known for over a century that El Niños do precisely the opposite, meaning they promote drought for total rainfall summed over the rainy season, June through September.”
El Niño occurs when ocean surface temperatures in the eastern equatorial Pacific Ocean are warmer than usual. While the climate event weakens the monsoon overall, Hill’s study showed that its effect on extreme rain is uneven across regions.
In central India and along the southwestern coast, rainfall became less frequent but more intense. In contrast, southeastern and northwestern regions saw a reduction in both total rainfall and extreme events. “The increases in extreme daily rainfall under El Niño compared to La Niña are concentrated in central India and the southwestern coastal band,” Hill explained. “In the southeast and northwest, the signal is opposite, meaning daily extreme rainfall is less likely.”
The findings shed light on why parts of India often experience devastating floods even during weak monsoon years. Extreme rain events have already caused widespread damage in recent decades. In 2024, floods and landslides killed more than 3,000 people, destroyed or damaged 230,000 homes, and wiped out nearly 10,000 head of livestock, according to government records.
“This raises the prospect of skillful ENSO-based seasonal forecasts of extreme rainfall probabilities within monsoonal India,” the study noted. ENSO, or El Niño–Southern Oscillation, is the scientific term that covers both El Niño and its counterpart, La Niña.
Co-author Michela Biasutti, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory, said the method used in the study made the differences clearer. “One key advance of our study’s approach is that, even though it deals with rare events, it allows robust differences to emerge without lumping all the data into a single ‘Indian rainfall’ bucket,” she said. “By doing so, we were able to see changes of the opposite sign in the rainiest and driest regions of the subcontinent.”
The research points to a new way of preparing for disasters. “Better predictions of when and where extreme rainfall events are likely to occur give society better chances to prepare, such as perhaps by earlier and better warnings or pre-mobilizing aid,” Hill said.
India, home to over 1.4 billion people, depends heavily on the summer monsoon. The rains feed crops, recharge rivers, and sustain water supplies. But they also bring hazards when extreme downpours overwhelm drainage systems, trigger landslides, and displace communities.
Hill stressed that the findings are not only relevant for India. Similar mechanisms could be at work in other tropical regions, where El Niño may also alter patterns of rainfall extremes. The study suggested that the framework used could be applied to other climate variability modes and to trends linked with global warming.
The work will continue under a new three-year, $408,862 grant from the U.S. National Science Foundation. Hill said the team will investigate how storms known as monsoon low-pressure systems behave differently under El Niño and La Niña conditions.
“Our results open the door to creating seasonal outlooks for extreme events in India, based on the slowly evolving temperature of the ocean,” Biasutti said. “This could improve the way we forecast hazards in a warming climate.”
The study challenges long-held assumptions and highlights a paradox: El Niño brings drier monsoons but sharper rainfall extremes. For India, that means preparing not just for less rain, but for sudden, destructive downpours that could strike during already difficult seasons.
Support us to keep independent environmental journalism alive in India.
Keep Reading
How Can Bhoj Wetland Address the Issue of Microplastics?
NGT Demands Report on Microplastic Pollution in Bhopal Lakes
Stay connected with Ground Report for underreported environmental stories.
Follow us on X, Instagram, and Facebook; share your thoughts at greport2018@gmail.com; subscribe to our weekly newsletter for deep dives from the margins; join our WhatsApp community for real-time updates; and catch our video reports on YouTube.
Your support amplifies voices too often overlooked, thank you for being part of the movement.
