South and Southeast Asia floods: A wake-up call for the region?

In recent weeks, countries in South and Southeast Asia have found themselves in the firm grip of a series of catastrophic typhoon, cyclone, and flood events.

Relentless rainfall events ranging from Sri Lanka to southern Thailand, central Vietnam, and western Malaysia, through to parts of the Philippines and western Indonesia, have triggered widespread flooding and landslides.

The full scale of the impacts is still emerging, though hundreds of thousands of properties have already been reported destroyed or damaged. With home insurance take-up rates in these areas some of the lowest globally, thousands of people will have been left displaced and financially deprived. As the rescue, relief, and recovery efforts continue, our thoughts are with those impacted by these devastating floods.

Cyclonic Storm Ditwah floods Sri Lanka

A short-lived and weak tropical cyclone during late November and early December, Cyclonic Storm Ditwah produced heavy rainfall, resulting in catastrophic flooding in Sri Lanka and parts of southern India. Making a brief landfall over Sri Lanka’s east coast, the system then moved back over the Bay of Bengal, but its slow track caused continuous rainfall across the country. Nearly one million people have been affected, and more than 400 have been reported dead.

Monsoon and typhoons swamp South and Southeast Asia

Turning to the Philippines, a country well versed in typhoon impacts at this time of year, having been hit by four typhoons in 10 days in November 2024, three tropical cyclones—Kalmaegi, Fung-Wong, and Koto—impacted the central and southern Philippines this November. The collective impact of Typhoons Kalmaegi and Fung-Wong and enhanced monsoon conditions has resulted in over 650,000 damaged properties and over 600,000 people displaced.

Central Vietnam became the focus of heavy rainfall toward the middle and end of November, as easterly winds transported the remnants of typhoons across the South China Sea toward central Vietnam; these combined and interacted with unseasonal cold air to produce continuous, torrential thunderstorms.

Rainfall totals during the event were extraordinary—most areas received 400–700 millimeters (15.7–22.6 inches), with some locations exceeding a meter (39.4 inches).

Stations in Phú Yên Province recorded totals exceeding 1.8 meters (73 inches), with Sông Hinh and Hòa Mỹ Tây also among the wettest locations, according to Vietnam’s National Centre for Hydro-Meteorological Forecasting.

Rivers across central Vietnam swelled to historic levels, including the Dinh Ninh Hòa, which exceeded its 1986 flood peak. Coastal provinces from Quảng Trị to Khánh Hòa were impacted, with additional impacts reported in the more inland, mountainous areas, including Đắk Lắk, Gia Lai, and Lâm Đồng.

The flooding has reportedly affected over 235,000 people, with more than 1,000 houses destroyed or severely damaged. Tragically, more than 90 people have lost their lives, with countless others displaced or left homeless.

Figure 1: Moody's RMS preliminary analysis of IMERG (NASA’s Integrated Multi-satellite Retrievals for GPM (IMERG), version 4.4 ) satellite precipitation shows the large areas affected by persistent and extreme rainfall events between November 16–30.

Already amidst a pronounced monsoon season, parts of the Malay Peninsula and the Indonesian island of Sumatra also experienced persistent heavy rainfall for several weeks in mid- to late-November, exacerbated by the rare development of a tropical cyclone over the region.

Cyclone Senyar formed over the Strait of Malacca on November 25. Its center tracked over Sumatra and then back east, over southern Thailand and the Malay Peninsula. While moderate in terms of its wind speeds, it brought torrential rainfall that exceeded local records and led to severe flash flooding and mudslides

In Hat Yai, the largest city in Thailand’s southern region (pop. ~190,000), rainfall totaled 370.2 millimeters (14.6 inches), equivalent to a 300-year rainfall return period. At least 162 people were killed, and more than 1.4 million households and 3.8 million people have been affected in Thailand’s twelve southernmost provinces, according to the country’s Department of Disaster Prevention and Mitigation.

Moving south across the border in Malaysia, flooding primarily impacted the northern and central states of the Malay Peninsula, including Kelantan, Perlis, Penang, and Perak.

The rural state of Kelantan bore the brunt of the impacts, with more than 8,000 people severely impacted, while 13,000 individuals across seven other states were evacuated to safety. Roads and communication networks were disrupted, and over 4,000 tourists became stranded in hotels due to rising floodwaters.

In Indonesia, more than 800 people have died, and at least 10,500 properties have been damaged or inundated across 51 districts in western Sumatra’s three provinces, according to Indonesia’s National Disaster Office; other estimates suggest damage numbers are several times higher. These events represent the country’s deadliest disaster since the 2018 Sulawesi earthquake and tsunami.

Figure 2: IMERG satellite precipitation over four South and Southeast Asia areas that experienced excessive rainfall for the period between November 16–30.

What caused the extreme rainfall?

According to the latest forecasts, as of early December, oceanic and atmospheric indicators suggest borderline La Niña conditions are present in the central equatorial Pacific.

Although sea surface temperatures are not yet at a stage for La Niña conditions to be officially declared, some atmospheric indicators suggest that parts of Southeast Asia are already experiencing La Niña-like conditions.

La Niña phases typically enhance convection over the Maritime Continent, representing the tropical region of islands in Southeast Asia and the western Pacific. This can strengthen monsoons in Southeast Asia and India, which collectively typically produce wetter-than-normal conditions in South and Southeast Asia.

This pattern has already been prevalent throughout November 2025 and provided a setup for the increased moisture and extreme rainfall totals across the region. On top of this, the several typhoons that impacted the Philippines, the rare cyclone over southern Thailand and Sumatra, and Ditwah in the Indian Ocean have all exacerbated the intensity and duration of extreme rainfall that resulted in major flooding in several locations.

A growing population exposed to floods

A study conducted by Moody’s found that the population at risk of flooding in Asia grew by over one billion people between 1975 and 2020. Over these 45 years, while the population has grown by about 95 percent, the population at risk of flooding has grown more, by about 130 percent, meaning the population at risk of flooding is growing faster than the actual population.

The study also found that based on the same 2020 census, almost 40 percent of Asia’s inhabitants are exposed to non-zero flood risk at the 100-year return period; the Asia-Pacific region overall is home to nearly 75 percent of the 2.44 billion people exposed to flooding at this 100-year return period.

A wake-up call for the region?

While the full extent and impact of the devastating flooding across Thailand, Malaysia, and Indonesia continue to emerge, early estimates suggest economic damages exceeding US$10 billion across the affected provinces.

Southeast Asia is no stranger to widespread flood events, but economic flood losses over the past 10 years have not exceeded US$1–2 billion. Only the 2011 Thailand floods were of a larger scale, with US$45 billion economic losses reported at the time.

This provided a wake-up call to the vulnerability of global technology supply chains and to the insurance industry's exposure to natural catastrophe losses in the region. More than 50 percent of the total losses were attributed to business interruption.

It is also possible that noticeable business interruption and supply chain losses may again occur in the region due to disruption to critical vehicle part manufacturing and transportation across the Malay Peninsula.

It is therefore not without reason that regulators across Southeast Asia are very actively monitoring and tightly regulating financial institutions' exposure to physical climate risk. For example, in their climate stress tests, the MAS (Monetary Authority Singapore) requires institutions to assess their risk across the full list of ASEAN-5 countries (Indonesia, Malaysia, Philippines, Singapore, and Thailand).

Understanding the full loss potential from flooding in Southeast Asia requires catastrophe modeling solutions that adequately consider event correlation. Moody’s RMS Southeast Asia Inland Flood Model is the only catastrophe model for the region that allows the assessment of flood risk correlation across Thailand, Indonesia, Malaysia, and Singapore.

It also explicitly captures temporal factors such as seasonality and the impact of climate variability (ENSO phases), and the model is being widely used by risk managers across the region.

Moody’s RMS Event Response clients can keep updated with the latest developments by accessing the Support Center here.