An Average Is Just an Average
First, it's crucial to understand what a “below-normal” monsoon really means. The India Meteorological Department (IMD) classifies the season based on its deviation from the Long Period Average (LPA), the mean rainfall received over the past 50 years.
A season is considered 'below normal' if the total rainfall across the country is between 90% and 96% of this average, and a 'deficiency' if it falls below 90%. However, this is a nationwide, four-month average. It’s a single number that smooths out massive variations in both time and space. A season can end with a deficit, yet still contain periods of extremely intense rainfall concentrated in specific areas. These deluges can cause widespread damage, but they may not be widespread or long-lasting enough to lift the country's overall seasonal average.
The Rhythm of the Monsoon: Active and Break Phases
The monsoon is not a continuous, four-month shower. It has its own rhythm, cycling between “active” and “break” phases. An active phase is a period of several days to a couple of weeks with widespread, heavy rains. A break phase, conversely, is a period of little to no rain over much of central India. A below-normal season is often characterized by prolonged or frequent break phases. However, the active phases, when they do occur, can be incredibly potent. Climate change is also believed to be making rainfall more erratic, leading to longer dry spells punctuated by short, sharp bursts of extreme rain. So, even if the dry 'break' periods dominate the season and pull the average down, a few highly intense 'active' spells can still bring destructive floods to some parts of the country.
The Rain-Makers: Monsoon Depressions
Much of the monsoon's most intense rainfall is delivered not by a gentle, widespread flow but by powerful, organised weather systems called monsoon depressions. These are low-pressure systems that typically form over the warm waters of the Bay of Bengal and move west-northwest across the country. They act like massive engines, pulling in moisture from the sea and unleashing torrential rain over hundreds of kilometres. A single strong depression can dump a huge amount of rain on eastern, central, and northern India in just a few days. A season might be weak overall due to a lack of these systems, but the formation of just one or two powerful depressions can cause localised, extreme rainfall events that lead to flooding even as other regions remain dry.
Location, Location, Location
The monsoon's behaviour is also heavily influenced by the position of the 'monsoon trough', an elongated low-pressure area that extends from the northwest to the Bay of Bengal. During active spells, this trough sits over the plains of India, bringing rain to the vast agricultural heartland. During a 'break', the trough shifts north to the foothills of the Himalayas. When this happens, rainfall stops over the plains but increases dramatically in the Himalayan foothills and Northeast India, sometimes causing flash floods and landslides in those regions. So while a farmer in Madhya Pradesh might be experiencing a drought-like situation, regions in the north and northeast could be facing a deluge—all part of the same 'break' in the monsoon.
The Problem on the Ground
This erratic pattern—long dry spells followed by sudden, heavy downpours—is the worst of both worlds for many. For farmers, it's a nightmare. They need consistent, moderate rainfall, not a cycle of drought and deluge that can damage crops. Urban areas are also hit hard. City drainage systems, often designed for more moderate rainfall, are easily overwhelmed by these intense bursts, leading to the severe waterlogging and flooding we increasingly see. Meanwhile, the long dry spells can strain water reservoirs, impacting drinking water supply and hydropower generation. This variability means that even in a 'below-normal' year, the country has to manage the twin crises of water scarcity in some parts and devastating floods in others.
