The Split Monsoon: How Changing Rainfall Patterns Are Reshaping India’s Climate

Syllabus areas:

GS Paper I: Geography

GS Paper III: Environment and Ecology

A 12–13% national rain shortfall hid a monsoon of record dry zones, wet corridors and sudden rain bursts

Despite a late burst of heavy rain, the 2026 southwest monsoon is shaping up to be India’s driest in 11 years. Last week’s deep depression brought widespread rain to parts of east, northeast, central and north India, cutting the season’s deficit from 15% to around 12% in a span of four to five days. But the monsoon is still set to be India’s first deficient season since 2015 and among the 10 weakest monsoons since Independence.

India Meteorological Department (IMD) classifies a seasonal rainfall deficit of 10% or more as ‘deficient’, its lowest rainfall category, commonly described as a monsoon drought.

The significance of this year’s rainfall deficit becomes clearer against the recent past. Five of the last seven monsoons produced either excess or above-normal rainfall. India appeared to have entered a relatively wet phase in its multi-decadal monsoon cycle, marked by fewer droughts.

This year has broken that run, with El Niño playing a major role. El Niño is the periodic warming of surface waters in the central and eastern equatorial Pacific that alters atmospheric circulation around the globe. The 2026 event is developing into the strongest on record.

The monsoon reached Kerala on June 4, just three days after the normal date, and initially advanced rapidly. By June 8, it covered much of southern India; by June 12, the northeast and much of eastern India were under monsoon winds. Then it stalled for nearly two weeks, reaching northwest India only in the first week of July.

With monsoon winds weak even where the system had arrived, June ended with a countrywide rainfall deficit of more than 35%, the highest in 12 years.

Bay of Bengal Lows on a High

The weakness persisted through the following months, but another feature of the monsoon changed: low-pressure systems (LPS) began repeatedly forming over the Bay of Bengal and moving inland, transporting moisture and producing heavy rain.

There were no such systems in June, but four in July, six in August and three in September, including the deep depression that crossed the north Andhra-south Odisha coast on Sept 23-24. Thirteen LPS during these three months is above normal 10-11.

The impact is visible on the district rainfall map (see graphic). A swathe of relatively good rainfall (blue and green) runs from parts of Rajasthan through Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Jharkhand, Gangetic West Bengal and Odisha. This is broadly the corridor through which many of the LPS travelled. Odisha, impacted by nearly all of these systems, witnessed its wettest monsoon in 20 years. This year’s June-Sept rainfall of over 1480mm is among the highest five the state had experienced since 1901.

Western disturbances, moist weather systems moving into north India from the Mediterranean region, also remained unusually active just as in recent years, which experts link to climate change. At times these WDs interacted with LPS, producing extreme rainfall, particularly in the Himalayan states.

The result is a strikingly uneven monsoon. As of Sept 25, 43% of India’s districts had received deficient or scanty rainfall, with most of the rainfall-starved districts concentrated in four broad clusters. Each of these clusters tells a story.

Punjab: Record Wet to Deficit

Punjab provides perhaps the sharpest year-to-year contrast. Its rainfall is currently 42% below normal, the largest sub-divisional deficit in the country and the state’s worst monsoon since 2004.

Just a year ago, Punjab received 621.6mm, or 41% above normal, its highest monsoon rainfall since 1988. Last year, floods and disease affected paddy yields in the state. This year, deficient rainfall could put both kharif and rabi crops under pressure while adding to the state’s already serious groundwater stress.

Countrywide, the 2026 monsoon may end with a 12-13% shortfall. But more than deficit, it is a story of a highly uneven monsoon: a weakened large-scale circulation, punctuated by bursts from smaller weather systems, with the result being islands of deluge amid large areas of drought.

West Rajasthan: A Rare Desert Drought

West Rajasthan, climatically the country’s driest subdivision, has recorded a rare 31% rainfall deficit. It is the subdivision’s first deficient monsoon in eight years and its lowest seasonal rainfall since 2009.

The contrast with recent history is striking. In the 17 monsoons since 2009, including 2026, west Rajasthan has averaged 25% above-normal rainfall. It recorded only two deficient seasons, alongside seven excess and two large-excess monsoons.

South: Driest in 24 Years

The largest rainfall-deficit zone stretches from southern Madhya Pradesh, Vidarbha and Madhya Maharashtra to Kerala and Tamil Nadu.

South India has a rainfall deficit exceeding 23%, making this its driest southwest monsoon since 2002. The district-level picture is starker: 88 of the region’s 147 districts, or 60%, had received deficient or scanty rainfall by Sept 27.

Rayalaseema in Andhra Pradesh has been particularly badly affected, with a deficit of 38%.

Bihar: Five Droughts in a Row

The most intense concentration of rainfall deficit in eastern India lies across Bihar and adjoining areas of eastern Uttar Pradesh and north Bengal.

As of Sept 27, 31 of Bihar’s 38 districts were rainfall-deficient. The state is on course for one of its seven driest monsoons since 1901 and is experiencing its fifth consecutive monsoon drought.

A 2024 CEEW (Council on Energy, Environment and Water, a public policy think tank) study of four decades of rainfall data found that during the 1982-2022 period, about 64% of Bihar’s tehsils had experienced declining rainfall in the months of June and July, while 40% recorded a fall of more than 10% across the full four-month monsoon season.

East & Northeast: Driest On Record

The East & Northeast region — comprising the seven subdivisions of Bihar, Jharkhand, Gangetic West Bengal, North Bengal & Sikkim, Assam & Meghalaya, Arunachal Pradesh, and other NE states of Nagaland, Manipur, Mizoram and Tripura — is heading for its driest monsoon since records began in 1901.

As of Sept 27, the region had received 1014.7mm against a normal 1,347mm, a deficit of nearly 25%. Even with the late-season rains, it will remain well below the previous record low of 1,069mm, set in 2013.

The decline is not confined to this year: IMD data shows that average monsoon rainfall in the region since 2000 is about 15% lower than during 1981-2000, and 26% below the peak reached during 1941-1960.

That is a substantial climatic shift, with potential implications for land use and ecology. Yet even during this exceptionally dry monsoon, parts of Assam and Nagaland suffered severe flooding. Experts have pointed to deforestation and development-related changes as factors that magnified the impact of the floods.

The 40-year signal behind this year’s swings

A 2024 study by researchers at the Council on Energy, Environment and Water (CEEW), which examined tehsil-level rainfall across India over four decades (1982-2022), found that short-lived wet extremes were contributing an increasing share of total monsoon rainfall, even though their intensity had not changed significantly. The study found that 64% of India’s tehsils experienced an increase in the frequency of heavy-rainfall days over the 40-year period.

In Decoding India’s Changing Monsoon Patterns: A Tehsil-level Assessment, the researchers used 1982-2022 as a baseline to assess changes during the subsequent decade, 2012-2022. Their map shows a significant increase in the frequency of heavy-rainfall days, defined as rainfall above the 90th percentile of all rainy days, across much of western India and nearly all of southern India.

With several exceptions, areas experiencing more heavy-rainfall days also saw an increase in very heavy rainfall events, defined as those above the 99th percentile, during 2012-2022. One finding is particularly striking: extreme rainfall events declined in most tehsils of Himachal Pradesh and Uttarakhand. Yet rain-related destruction in both states has increased in recent years. This suggests that rainfall extremes alone cannot explain the growing damage. Encroachment, unplanned urbanisation, altered drainage, deforestation and large infrastructure projects may be turning heavy rain into increasingly destructive events.

The changing monsoon, therefore, is not simply a story of more or less rain. It is increasingly one of when, where and how quickly that rain arrives — and why it’s having a disproportionately destructive impact in India.

The trend was markedly different across most of east and northeast, and parts of central and northwest India. Heavy-rainfall days declined in much of eastern Madhya Pradesh, Chhattisgarh and interior Odisha, as well as parts of Haryana, Himachal Pradesh and Uttarakhand and nearly all of Uttar Pradesh.

The deep depression that struck the Andhra-Odisha coast on Sept 23-24 is bringing heavy rainfall to more than 10 meteorological subdivisions across India. Over the five days of its impact, rainfall from the system is, by a rough estimate, expected to amount to 20-30% of the country’s normal rainfall for Sept. That is monsoon variability in a nutshell: more rain in five days near the end of the season than the country received during the preceding 10-12 days.

Because the monsoon is driven by a complex interplay of atmospheric and oceanic processes, considerable natural variability is inevitable, both in where and when rain falls. But there is growing evidence that climate change is amplifying this variability, with extreme rain events of the kind produced by the recent depression becoming more frequent.

Courtesy – The Times of India