Understanding Heavy Rainfall Events in India During El Niño Years
Introduction
The widespread heavy rainfall observed across India during the past few days provides a clear example of this apparent paradox (Figure 1).
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| Figure 1: 24-Hour Cumulative Rainfall Recorded over Different Stations of India at 8.30 IST on 6 July 2027. [Source: IMD] |
Why Can Heavy Rainfall Occur During El Niño?
The seasonal outlook issued before the monsoon indicated that El Niño conditions are likely to suppress the seasonal rainfall over India, increasing the probability of below-normal monsoon rainfall. This expectation remains scientifically valid because El Niño typically weakens the large-scale monsoon circulation.
However, weather during the monsoon is controlled not only by seasonal-scale climate drivers such as El Niño but also by synoptic weather systems (low-pressure systems, depressions, monsoon troughs) and intraseasonal oscillations such as the Madden-Julian Oscillation (MJO) and Monsoon Intraseasonal Oscillation (MISO). When these weather systems interact favourably with the background monsoon circulation, they can produce intense rainfall over localized regions irrespective of whether the seasonal monsoon is expected to be wetter or drier than normal.
The recent rainfall episode illustrates this distinction between seasonal climate and day-to-day weather. Although India entered July with a substantial seasonal rainfall deficit, several parts of western, central and eastern India experienced heavy to extremely heavy rainfall during just a few days. As shown in the daily rainfall analysis:
This demonstrates that a few days of widespread intense rainfall can substantially alter seasonal rainfall statistics, even though the seasonal outlook itself has not fundamentally changed.
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Figure 2. Daily and cumulative all-India rainfall during the 2026 southwest monsoon (up to 6 July 2026) compared with the 1971–2020 climatological normal. |
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| Figure 3. Spatial distribution of observed 24-hour rainfall on 6 July 2026, the corresponding climatological normal, and rainfall anomaly. |
Lessons from Past El Niño Years
The recent heavy rainfall episodes are not unprecedented. Historical observations show that many major El Niño years have witnessed widespread heavy rainfall events over different parts of India, even though the seasonal monsoon rainfall was below normal on average. Figure 4 illustrates the spatial distribution of heavy rainfall days during major El Niño years since 1982. While the intensity and location of these events vary from one El Niño episode to another, the maps consistently reveal that extreme rainfall can occur over several regions of the country during El Niño years. This highlights an important aspect of the Indian summer monsoon: a weaker seasonal monsoon does not necessarily imply fewer heavy rainfall events or a lower flood risk.
Although El Niño influences the seasonal mean monsoon circulation, the occurrence of individual heavy rainfall events is primarily governed by synoptic weather systems and intraseasonal variability. Consequently, seasonal rainfall deficits and short-duration extreme rainfall events can coexist.
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Figure 4. Spatial distribution of heavy rainfall days (≥64.5 mm day⁻¹) during major El Niño years (1982–2023). Despite below-normal seasonal monsoon rainfall, heavy rainfall events occurred across many parts of India during major El Niño years. |
Impacts of Heavy Rainfall Events
The distinction between seasonal rainfall and extreme rainfall is not merely a scientific concept—it has important implications for disaster risk management, agriculture, water resources, and urban planning. Seasonal rainfall totals alone are often insufficient for planning and decision-making. A district may receive near-normal seasonal rainfall by the end of the monsoon, yet still experience severe flooding because much of the rainfall occurred within only a few intense events. Conversely, another region may remain drought-prone despite these localized extreme rainfall events occurring elsewhere. Therefore, adaptation and preparedness must consider rainfall variability across multiple timescales—from seasonal outlooks to sub-seasonal, daily, and even hourly forecasts.
Summary
An El Niño year should never be interpreted as a "no-flood" year. Although El Niño increases the likelihood of below-normal seasonal monsoon rainfall over India, it does not eliminate the possibility of extreme rainfall events. Favourable synoptic weather systems and intraseasonal variability can still produce short-duration, high-intensity rainfall capable of causing floods, landslides and urban inundation. The recent rainfall episode serves as a reminder that seasonal rainfall deficits and extreme rainfall events can coexist. Therefore, effective disaster preparedness requires integrating seasonal climate outlooks with sub-seasonal and short-range weather forecasts to provide timely early warnings and support climate-resilient decision-making.
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Disclaimer: The views and interpretations presented in this blog are solely those of the author and are intended for educational and science communication purposes. They do not necessarily represent the official views, policies, forecasts, or positions of the India Meteorological Department (IMD) or any other organization with which the author is affiliated.
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