The recent overlapping tropical storms and intense monsoon activity in Southeast Asia that began in November 2025 have affected over 11m people, leading to economic losses of over $30bn. The catastrophic events were driven by an unusual convergence of powerful weather systems in the region.
Sri Lanka and India
According to Aon in its latest "Weekly Cat Report" dated 5 December 2025, cyclone Ditwah primarily impacted Sri Lanka and the southern states of India.
In Sri Lanka, preliminary estimates have estimated direct damage from Ditwah at between $613–835m with agricultural losses also extremely high at an additional sum of around $556m. Combined with indirect economic losses, the event’s total damage is estimated to account for around 0.75–1% of the country’s GDP. The economic losses in Sri Lanka are estimated to be around $7bn.
The cyclone also affected over 1.5m people in the island nation. It caused 481 fatalities, becoming the country’s deadliest cyclone since 1978 and the third deadliest in its history.
Infrastructure impacts included widespread road and rail blockages, breaches at the Mavil Aru dam, a shutdown of two major hydropower plants, and power outages affecting 25–30% of the region.
In India, losses were estimated at around $40m. The cyclone caused at least three deaths in the country and damaged 57,000 ha of agricultural land, along with material losses along the coastal areas of Tamil Nadu.
The Philippines and Vietnam
Typhoon Koto in late November 2025 primarily affected the Philippines and Vietnam. Typhoon Koto by itself did not lead to any significant economic losses in either country, though people were impacted due to the cyclonic activity.
The typhoon in the Philippines was relatively benign compared to other typhoons this year, though it affected over 275,000 people.
In Vietnam, cyclonic activities during 2025, including Koto and earlier storms, have caused total economic damages exceeding $3.2bn. The Nat CAT events (till November 2025) took a toll of 409 lives and many more were injured or are reported missing.
Thailand, Indonesia and Malaysia
Further south, tropical storm Senyar caused extensive flooding in southern Thailand, Peninsular Malaysia, and Indonesia (Sumatra). The economic losses in the three countries due to storm Senyar are estimated to be at least $19.8bn.
Thailand
In Thailand, government estimates have put the economic losses at over $15.7bn.
The Aon report said that according to Thailand’s Department of Disaster Prevention and Mitigation, a total of 22 provinces had reported flooding over the course of these events. At the height of these events in south Thailand, about 1.5m households (over 4m people) were impacted by flooding. In addition to extensive infrastructure damage in Thailand, the cumulative death toll has risen to 306 people.
Indonesia
According to reports issued by Indonesia’s National Board for Disaster Management (BNPB), losses in Indonesia due to the recent tropical storms have been substantial. Losses related to cyclonic flooding are estimated to be over $4.1bn.
In Aceh Province, an estimated 46,000 homes have been damaged, alongside significant impacts to infrastructure. In terms of the death toll, current consolidated figures for North Sumatra, West Sumatra, and Aceh indicate at least 836 fatalities, around 2,600 injured, and 518 people still missing. According to official data, cyclone Senyar is now the second-deadliest tropical cyclone in the nation’s history, only behind the 1973 Flores Cyclone (1,650 fatalities).
Malaysia
Malaysia was spared from severe flooding. However, the event affected 10 states across the country, displacing more than 21,000 people nationwide. The death toll has risen to three as of 5 December 2025. The cyclonic activity also disrupted transportation and overwhelmed flood mitigation systems, particularly in the state of Selangor.