When Below-Average Rains Don’t Mean Safety, India’s Rising Threat of Extreme Rainfall Events
The popular imagination often associates flooding with excessive rainfall. A good monsoon, in the public mind, means plenty of water, potential floods, and the need for vigilance. A below-average monsoon, by contrast, suggests drought, water scarcity, and relief from flood threats. This intuition, however, is increasingly at odds with the scientific reality of India’s changing climate. The data from the India Meteorological Department (IMD) reveals a paradox: the overall extent of monsoon rain has had no bearing on the frequency or severity of extreme rainfall events. Even in years when the total seasonal rainfall is deficient, the number of days with “extremely heavy rain”—defined as more than 21 cm (204.5 mm) in a 24-hour period—has been rising. Starting with the Kedarnath tragedy in 2013, India has seen at least one major rainfall-related disaster every year. The threat is not from the total volume of rain; it is from its intensity, its concentration, and its unpredictability.
The Changing Definition of “Extremely Heavy”
The IMD classifies any rainfall above 21 cm in a 24-hour period as extremely heavy rain. Typically, such events account for less than 0.1 per cent of all recorded rainfall events in the country. But their number seems to be increasing. Importantly, part of this rise can be attributed to a lowering of the threshold for a rainfall incident to qualify as extremely heavy. Before 2016, only rainfall above 244.5 mm in a 24-hour period was classified as extremely heavy. This was lowered to 204.5 mm (sometimes rounded off as 21 cm) in 2016. However, the increasing trend of such incidents is evident even at the higher threshold level. The problem is not merely definitional; it is real.
In the four-year period between 2008 and 2011, the maximum number of extremely heavy rainfall events in any season was 64 (in 2008), according to IMD’s Annual Monsoon Reports. This number has been consistently above 100 every year since 2017. In 2024, as many as 181 extreme rainfall events were recorded, while in 2025, this number was 160. The trend is unmistakable and deeply concerning. More stations are reporting record-breaking rainfall events year after year.
The Historical Record: A Disaster Every Year Since 2013
Starting with the Kedarnath tragedy in 2013, India has seen at least one major rainfall-related disaster every year. The list is a grim roll call of devastation: 2013 Kedarnath (Uttarakhand), 2014 Kashmir flooding, 2015 Chennai floods, 2016 Bengaluru rains, 2017 Gujarat floods, 2018 Kerala floods and Wayanad landslides, 2019 Maharashtra floods (Kolhapur, Pune), 2020 Hyderabad floods, 2021 Assam floods, 2022 Himachal Pradesh and Delhi floods, 2025 (again) Kedarnath disaster. The geography of these events spans the entire country—from the Himalayas to the coasts, from the deserts to the deltas. No region is immune.
The 2018 Kerala floods were particularly devastating. The state received 42 per cent more rainfall than the average during the monsoon season, but the disaster was triggered by a series of extreme rainfall events in August. The dams filled rapidly, and the release of water compounded the flooding downstream. Over 400 people died, and more than a million were displaced. The economic losses ran into thousands of crores.
The 2015 Chennai floods were another wake-up call. The city received 340 mm of rain in a single day (December 1, 2015), the highest in over a century. The urban drainage system, designed for much lower intensities, was overwhelmed. The Adyar and Cooum rivers overflowed. The airport was closed. Over 400 people died. The event highlighted the vulnerability of India’s cities to extreme rainfall, even in a region not typically associated with such intense downpours.
The Paradox: Below-Average Rains, Above-Average Danger
The key insight from the data is that the overall extent of monsoon rain has no bearing on the frequency or severity of extreme rainfall events. A year with a below-average monsoon can still produce several days of extremely heavy rain, concentrated in a few locations or a few hours. These concentrated bursts are what trigger landslides, flash floods, and urban flooding.
Consider the 2025 Kedarnath disaster. The overall monsoon rainfall in Uttarakhand was not exceptional. But a single extreme rainfall event in the catchment area of the Mandakini river triggered a massive landslide and flash flood, washing away infrastructure and claiming lives. The lesson is stark: it is not the amount of rain that falls over the season that matters; it is the amount that falls in a day, or even in an hour.
This has profound implications for disaster preparedness. Traditional early warning systems based on seasonal forecasts or weekly totals are inadequate. What is needed is real-time, high-resolution forecasting of extreme rainfall events at the scale of a few kilometres and a few hours. And even when such forecasts are available, the response must be swift: evacuations, closure of roads and schools, deployment of rescue teams.
The Difficulty of Prediction: Why Extremely Heavy Rain Catches Us Off Guard
Such extraordinary high rainfall is extremely difficult to predict. The IMD can see the chances of very heavy rainfall and issues appropriate alerts, but whether the event will occur depends on a range of factors that are not fully captured by current models. The scale is small—often less than 100 km across—and the lead time is short—often less than 24 hours. By the time the alert is issued, it may be too late to evacuate vulnerable populations.
Climate change is making prediction even harder. Warmer air holds more moisture. For every 1 degree Celsius of warming, the atmosphere can hold 7 per cent more water vapour. This means that when conditions are right for rainfall, the potential intensity is higher. The same synoptic system that would have produced moderate rain a few decades ago can now produce extreme rain. This “loading” of the atmosphere is well understood, but the spatial and temporal distribution of the resulting rainfall remains highly uncertain.
The IMD has improved its forecasting capabilities significantly over the past decade. It now uses high-resolution models, Doppler weather radars, and satellite data to issue district-level warnings. But the inherent unpredictability of extreme rainfall events means that there will always be false alarms and missed events. The challenge is to build a system that is resilient to both.
Regional Patterns: Assam, Bengaluru, Mumbai, and Beyond
The increasing intensity of extreme rainfall events is evident across various regions, particularly in Assam, Bengaluru, Mumbai, and the Western Ghats. In Assam, the Brahmaputra river has been flooding with increasing frequency, exacerbated by extreme rainfall in its catchment areas in India and China. In Bengaluru, rapid urbanisation has destroyed natural drainage systems, turning moderate rain into urban floods. In Mumbai, the 2005 deluge (944 mm in 24 hours) was once considered a once-in-a-century event; now, such intensities are becoming more common.
In 2016, the state of West Bengal experienced a significant increase in rainfall intensity. The monsoon season typically lasts from June to September, but the intensity of rainfall during this period was particularly high. As a result, the state experienced severe flooding in several districts, including parts of West Bengal, Bihar, Jharkhand, Odisha, and Andhra Pradesh. The floods caused extensive damage to property and infrastructure, leading to loss of lives and livelihoods. The pattern repeated in subsequent years, with different regions bearing the brunt each time.
The Government Response: Early Warnings and Mitigation
The government has taken steps to mitigate the impact of these events. For instance, the National Disaster Management Authority (NDMA) has launched a campaign to raise awareness about the risks associated with extreme weather events. Additionally, the state has established early warning systems to alert people in advance of impending storms. These measures have helped to reduce the severity of the impact of the floods in some cases, but much more needs to be done.
The Sendai Framework for Disaster Risk Reduction, to which India is a signatory, emphasises the need for a shift from reactive disaster response to proactive risk reduction. This requires investments in infrastructure: drainage systems, embankments, flood shelters, and early warning systems. It also requires land-use planning: avoiding construction in floodplains and landslide-prone areas. It requires community preparedness: drills, evacuation plans, and stockpiles of emergency supplies. And it requires governance: coordination between central, state, and local authorities, with clear lines of responsibility.
Conclusion: The New Normal
The data from the IMD is clear: extreme rainfall events are becoming more frequent and more intense. The number of stations reporting record-breaking rainfall events has risen from 89 in 2016 to 166 in 2025 (and 181 in 2024). This is not a blip; it is a trend. And it is a trend that is projected to continue as the climate warms.
India cannot prevent extreme rainfall events. But it can prepare for them. It can build resilient infrastructure. It can improve forecasting and early warning. It can educate citizens on what to do when the waters rise. And it can learn from past disasters, instead of repeating the same mistakes.
The popular imagination equates below-average rains with safety. That is a dangerous illusion. In a changing climate, the threat is not from the total volume of rain; it is from its intensity, its concentration, and its unpredictability. Even a dry monsoon can bring a deadly downpour. India must be ready.
Q&A: Extreme Rainfall Events and Flood Threats in India
Q1: What is the paradox highlighted by the article regarding the relationship between overall monsoon rainfall and extreme rainfall events?
A1: The paradox is that the “overall extent of monsoon rain has had no bearing on the frequency or severity of extreme rainfall events.” Popular intuition assumes that a below-average monsoon means drought and reduced flood risk, while an above-average monsoon means higher flood risk. The data shows that this is false. Even in years when the total seasonal rainfall is deficient, the number of days with “extremely heavy rain” (more than 21 cm in 24 hours) has been rising. The threat is not from the total volume of rain over the season, but from its intensity, concentration in a few hours or days, and unpredictability. The 2025 Kedarnath disaster occurred in a year when overall monsoon rainfall in Uttarakhand was not exceptional—but a single extreme event triggered catastrophic flooding and landslides.
Q2: What is the threshold for “extremely heavy rain” according to the IMD, and how has the number of such events changed over time?
A2: The IMD classifies any rainfall above 21 cm (204.5 mm) in a 24-hour period as extremely heavy rain. In the four-year period between 2008 and 2011, the maximum number of extremely heavy rainfall events in any season was 64 (in 2008) . This number has been consistently above 100 every year since 2017. In 2024, as many as 181 extreme rainfall events were recorded, while in 2025, this number was 160. The number of stations reporting record-breaking rainfall events has risen from 89 in 2016 to 166 in 2025. Importantly, the increasing trend is evident even at the higher pre-2016 threshold of 244.5 mm, confirming that the rise is not merely due to a definitional change.
Q3: Can you list some of the major rainfall-triggered disasters in India since 2013?
A3: Starting with the Kedarnath tragedy in 2013, India has seen at least one major rainfall-related disaster every year:
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2013: Kedarnath (Uttarakhand)
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2014: Kashmir flooding
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2015: Chennai floods
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2016: Bengaluru rains
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2017: Gujarat floods
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2018: Kerala floods and Wayanad landslides
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2019: Maharashtra floods (Kolhapur, Pune)
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2020: Hyderabad floods
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2021: Assam floods
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2022: Himachal Pradesh and Delhi floods
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2025: Kedarnath disaster (again)
The geography of these events spans the entire country, demonstrating that no region is immune to extreme rainfall threats.
Q4: Why are extremely heavy rainfall events so difficult to predict, and what are the implications for disaster preparedness?
A4: Such extraordinary high rainfall events are “extremely difficult to predict” because the spatial scale is often small (less than 100 km across) and the lead time is short (often less than 24 hours). The IMD can see the chances of very heavy rainfall and issue appropriate alerts, but whether an extreme event will occur depends on a range of factors not fully captured by current models. Climate change makes prediction even harder: warmer air holds more moisture (7 per cent more per 1°C of warming), “loading” the atmosphere for higher intensity rainfall when conditions are right. The implication is that traditional early warning systems based on seasonal forecasts or weekly totals are inadequate. What is needed is real-time, high-resolution forecasting at the scale of a few kilometres and hours, combined with swift response capabilities (evacuations, road closures, deployment of rescue teams). The inherent unpredictability means there will always be false alarms and missed events, requiring a system resilient to both.
Q5: What steps has the government taken to mitigate the impact of extreme rainfall events, and what more needs to be done?
A5: The government has taken some steps: the National Disaster Management Authority (NDMA) has launched awareness campaigns about extreme weather risks, and early warning systems have been established to alert people in advance of impending storms. These measures have helped reduce the severity of impacts in some cases, but “much more needs to be done.” The article recommends a shift from reactive disaster response to proactive risk reduction, aligned with the Sendai Framework. This requires:
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Infrastructure investments: Drainage systems, embankments, flood shelters, and early warning systems.
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Land-use planning: Avoiding construction in floodplains and landslide-prone areas.
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Community preparedness: Drills, evacuation plans, and stockpiles of emergency supplies.
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Governance: Coordination between central, state, and local authorities with clear lines of responsibility.
The article concludes that while India cannot prevent extreme rainfall events, it can prepare for them. The popular belief that below-average rains mean safety is a “dangerous illusion.” Even a dry monsoon can bring a deadly downpour. India must be ready.
