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Assam is no stranger to pre-monsoon rainfall. But that may be changing soon. On May 29, the deep depression over coastal Bangladesh and West Bengal was slowly weakening and forming a well-marked low-pressure area over parts of Northeast India. However, by May 31, the region’s largest city of Guwahati recorded its highest May rainfall as recorded by the local meteorological department, drowning half of the city.
On June 2, close to 515,000 people in Assam were impacted by floods and the state recorded a death toll of seven, including two children — with dam-induced floods impacting almost half of the flood-affected people.
As of June 2, Assam lost 12,610.27 hectares of standing paddy crop, jute and various pulses to these floods with 31,212 persons being housed in 322 government relief camps. Besides, there are 154,000 people seeking relief from various relief distribution centres across the state.
The Assam government has estimated that 1,000 animals, mostly livestock, have been washed away by the torrents of floods impacting 460,000 animals. These floods have also started impacting wildlife by flooding 53 of 233 camps inside the Kaziranga National Park and Tiger Reserve.
The state government has deployed 122 medical teams with 50 boats to carry out rescue operations in the flooded expanse as 11 rivers, including the Brahmaputra and Barak and their tributaries, continue to flow above the danger mark. According to the Assam government, 65 revenue circles have been submerged by floods as rains continue in several parts of the state. On the other hand, the Brahmaputra’s waters, coupled with urban flooding, has impacted 18 municipal wards in Guwahati city alone.
The Silchar-Vangaichungpao Passenger Train, under the Northeast Frontier Division of the Indian Railways, was cancelled.
Between May 30 and May 31, Guwahati recorded around 111 millimetres (mm) of rainfall in 24 hours, with rains starting early on May 30 along with other parts of the state. The earlier record is also from the month of May 2025, when rain gauges at Guwahati’s Lokapriya Gopinath Bordoloi Airport measured 99.6 mm on May 20, breaking the 1958 record of 96.8 mm.
By May 30 evening, the city’s low-lying neighbourhoods were quickly flooded while several landslides and flash floods were reported from the hills surrounding it. The city came to a standstill, with arterial roads clogged by people rushing out of their workplaces due to various construction works like flyovers by the Assam government. Even Assam’s Chief Minister, Himanta Biswa Sarma was stranded in the waterlogged city roads on May 31. Angry residents burnt the effigy of the state’s Minister of Public Health Engineering, Jayanta Mallah Baruah. “They have built drains with no outlets in our area and there is sewage flowing through our houses. They are building flyovers which is bringing in more silt from the construction sites to our neighbourhood while flood preparedness at the city level is almost zero. Is this what you call a Smart City?” roared an angry resident of Rukminigaon, one of the worst affected neighbourhoods of the city.
Although the India Meteorological Department (IMD) ascribes the present extreme rainfall event to the upper-air cyclonic circulations and low-level troughs fuelling an unstable weather pattern, scientists in Assam have uncovered an unusual pattern in pre-monsoon rainfall impacting Northeast India over the years.
“Recently cyclonic conditions were observed in western coast states like Goa and Karnataka which brought copious amounts of moisture and heavy rainfall. Similarly, due to global warming, sea surface temperatures have gone up. We have noticed some serious storm formations over the region and there was warm air in the lower level of the atmosphere and cool air in the upper levels. There were abnormally higher amounts of moisture at the lower level, measuring up to 20 grams per kilogramme. We have been studying storms in the pre-monsoon period. We found that more pre-monsoon storms happen in May instead of April. These storms release a huge amount of latent heat in the upper atmosphere. The Tibetan Plateau is also heated up around this time. This latent heat from the storms, as well as the prevailing heat, causes monsoons to arrive much earlier. We will soon be publishing our findings. But it seems climate change is shifting the southwest monsoon to May in Northeast India,” Rahul Mahanta, an Associate Professor of physics at Guwahati’s Cotton University and also, a well-known climate scientist, told Down To Earth (DTE).
Between May 30 and June 1, the low-pressure area moved further eastwards, causing untold devastation in hilly areas like the Karbi Anglong and Cachar districts and bringing cities like Silchar to a grinding halt. Between May 31 and June 1, the second-largest city of Assam, Silchar received 415.8 mm rainfall in 24 hours. This broke the 132-year-old record of 290.3 mm rainfall in a day. On June 2, when the state disaster management agency compiled the data, Sribhumi (formerly Karimganj) bordering Bangladesh remains one of the worst-hit districts with 289 villages fully submerged by the waters of the Barak river and its smaller tributaries.
Pre-monsoon rainfall had already started across the hilly expanse of states like Arunachal Pradesh since the beginning of May. Between May 29 and May 30, extremely heavy rainfall was witnessed in the upper reaches of Ranganadi, a tributary of the Brahmaputra that flows through North Lakhimpur. The only hydropower generating mega dam in Arunachal Pradesh, the Ranganadi Hydroelectric Project on the Panyor river, opened all its four sluice gates during the wee hours of May 31 as it rained heavily in the catchment area. Within five hours, five of seven revenue circles were under water impacting 95 villages in Lakhimpur district.
NEEPCO, a government-owned power utility, claims that it messaged the deputy commissioner of Lakhimpur district about the water release. For the last few years, NEEPCO set up an alarm system that alerts the downstream villages on the dam water release.
On May 31, locals however were caught unawares about the incoming deluge. Montu Saikia, a grassroots social worker and a resident of Kharkati, one of the badly affected areas in Nowboicha circle of Lakhimpur district received the message at 1 am when the authorities opened the gates.
“The message said all the four gates would be opened. The rains started much earlier on May 30. A local media outlet quoting NEEPCO and local administration sources said two gates of the dam will be opened. Over the years, we know how much water can come with the knowledge of the number of gates which are opened in the dam site. The message from the administration was confusing for many so they could not save their belongings,” Saikia told DTE.
Saikia added that even the traditional Mising houses usually constructed on stilts at six to eight feet above the ground by the Assam plains tribe had water flowing above the roof. The same story is repeated on the south bank of the Brahmaputra in Nagaon district, where dams built by NEEPCO in Karbi Anglong flooded four of seven revenue circles.
Civil society members came down heavily against the lack of coordination between the dam operators and the local administration in the aftermath of the disaster. “There must be strict accountability of hydropower project authorities, both public and private. The sudden release of water from dams without adequate prior warning is unacceptable. We call for joint impact assessments with the involvement of government bodies, scientific and research institutions and civil society to document damage, displacement, and long-term risks such as siltation and erosion. Affected communities, particularly indigenous groups, small farmers and daily wage workers must receive timely and transparent compensation and support for livelihood recovery. We urge the state and central governments to undertake a comprehensive review of hydropower policies in Northeast India, conduct independent dam safety audits and reassess the cumulative environmental impacts in fragile and disaster-prone areas,” Tirtha Prasad Saikia, the director of North-East Affected Area Development Society (NEADS) told DTE.