Limp monsoon that left swathes of India bone dry | Number Theory

Wednesday marked the end of the four-month-long southwest monsoon, which normally accounts for 75% of India’s annual rainfall. Wednesday marked the end of the four-month-long southwest monsoon, which normally accounts for 75% of India’s annual rainfall. How was the rainfall performance this season? Bad is the short answer, with total monsoon rainfall being the 17th lowest since 1901 (earliest available data). This detailed analysis explains exactly what this entails.Total monsoon rainfall received is the 17th lowest since 1901 (earliest available data) (Unsplash)A month of surplus rain did not ease the El Nino painAn early El Nino—a cyclical warming of the central eastern equatorial Pacific Ocean that crimps monsoon rain—meant that rainfall would be underwhelming. According to the India Meteorological Department’s (IMD) real-time gridded data, India received 767mm rainfall this monsoon in terms of area weighted average. This is the 17th lowest monsoon rainfall for since 1901 and 10.5% below the 1971-2020 average for the same period, which IMD currently considers as the Long Period Average (LPA) for tracking monsoon rain. This also makes the 2026 monsoon the driest since 2009, when India got 722mm rain by weighted average. Only July recorded a surplus this monsoon, although the deficit was relatively small in September too. To be sure, IMD’s published statistics may show slightly different numbers because they use a somewhat different method for computing India averages.39% of the country’s area has drought-like conditionsThere is no uniform definition of drought in India. This is because the term has practical implications for agriculture, and vegetation stress is not guided by rainfall alone. One rainfall-based definition sometimes used in Mausam (the quarterly research journal of IMD) defines a 26%-50% rainfall deficit over LPA as a “moderate” drought and more than 50% deficit as a “severe” drought. The gridded data shows that 39% of the country is in drought, with 11.7% in the severe range. The area under drought is the 17th highest since 1901 and the area under severe drought is the 25th highest.Long dry spells were the norm in western and peninsular IndiaThis can be seen by tracking dry days or days of rain under 2.5mm. Parts of Tamil Nadu, Andhra Pradesh, Karnataka, Maharashtra, Gujarat, and Rajasthan saw the longest dry spell – consecutive dry days – stretch longer than 50 days. At least half of the area of most states also saw more dry days this monsoon than in the 1971-2020 average. The only exceptions were Uttar Pradesh, West Bengal, and Madhya Pradesh among big states, and even here, 39%-48% of the area saw more dry days than normal.Low-pressure systems kept parts of eastern and central India wetWhile a drought-like dryness leads to water stress, it does not mean agriculture will be completely doomed. Some parts, such as the Indo-Gangetic plains, are well-irrigated. On the other hand, parts of these plains faced floods. IMD defines a surplus of 20%-59% as “excess” and of at least 60% as “large excess”. Deficits of the same degree are called “deficient” and “large deficient”, with deviation up to ±19% of LPA called “normal”. 52.7% of the country ended up in the normal and excess categories for June-September. But that was because of monsoon low-pressure systems that travelled from the Bay of Bengal to bring excess rain in the July-September period. Odisha and parts of Chhattisgarh, Madhya Pradesh, and Uttar Pradesh were the most affected by storms of this kind. Another peculiarity this monsoon was the flooding in Bihar, though most of the state was deficient even from July to September. This was because of floods in rivers and tributaries that flow to the state either from Nepal or its neighbouring states. This means crop damage and likely headwinds to farm incomes and tailwinds to inflation not just on account of low rain but also more rain than what was needed. Abhishek Jha is Assistant Editor-Data at Hindustan Times. He uses statistical programming to generate newsworthy insights from large datasets. He is part of the team that produces Number Theory, a daily data story feature of the paper’s print edition. Since March 2024, he has been writing Weather Bee, a weekly column for the Hindustan Times website. He is a chemical engineer by training, who specialises in stories related to weather, climate, and the environment. Jha has been at HT since 2018, where he offers data-driven perspective and analysis on politics, environment, weather, climate, economy and society. His work includes data coverage of elections in India and abroad, including the 2019 and 2024 Lok Sabha elections; the disasters and extreme weather resulting from changing climate, such as floods, droughts, heat waves, cold waves, and dwindling snow cap in the Himalayas; the factors that drive poor air quality in northern India; the changing patterns of land use; the Covid-19 pandemic and its impact on labour market conditions; the changing pattern of consumer spending seen in the new consumer spending surveys; and social norms seen in the surveys such as the National Family Health Survey.Read MoreAkshay Deoras is a research scientist at the National Centre for Atmospheric Science & Department of Meteorology, University of Reading, UK.Read MoreNumber TheoryGet the latest India News, breaking headlines, and real-time updates from across the nation. Stay informed on politics, government policies, crime, weather, and major national developments.