Thailand on alert for heavy rain with tropical storm possible
Thailand faces heavy to very heavy rain through September 13, with Bangkok, the East and the South at risk while a South China Sea low may become a tropical storm.
- Thailand's meteorological department has issued a warning for heavy to very heavy rain across the country, with impacts expected until 13 September.
- An active low-pressure cell over the South China Sea is likely to strengthen into a tropical storm, which is forecast to move towards the coast of northern Vietnam.
- The public has been warned of the risk of flash floods and runoff, particularly in low-lying areas and near waterways.
The Thai Meteorological Department (TMD) issued its eighth advisory on Thursday (September 10), warning of heavy to very heavy rain across Thailand, with impacts expected through September 13.
On September 10, heavy to very heavy rain is forecast in parts of the North, Northeast, Central region, including Bangkok and its vicinity, the East and the South. The conditions are being driven by a high-pressure system or cold air mass that has extended over the upper North and upper Northeast.
This has pushed the monsoon trough southwards across the lower North, upper Central region and lower Northeast towards an active low-pressure cell over the central South China Sea. Meanwhile, a moderate southwest monsoon is prevailing over the Andaman Sea, the South, the Central region and the East region, and the Gulf of Thailand.
From September 11 to 13, rainfall is expected to increase in the South, with heavy to very heavy rain in some areas, while the North and Northeast are forecast to receive less rain. Heavy rain will remain possible in parts of the Central region, including Bangkok and its vicinity, and the East.
A high-pressure system or cold air mass from southern China is expected to extend over the North and upper Northeast, pushing the monsoon trough southwards across the lower Central region, the upper Gulf of Thailand, the East and the lower Northeast towards the active low-pressure cell over the central South China Sea.
The southwest monsoon over the Andaman Sea, the South and the Gulf of Thailand is also expected to strengthen.
The department urged the public to remain alert to heavy to very heavy rain and accumulated rainfall, which could trigger flash floods and runoff. Particular caution is advised in foothill areas near waterways and in low-lying areas.
People should avoid travelling on routes prone to repeated flooding, particularly in low-lying areas where temporary inundation may occur.
Tropical storm may develop over South China Sea
From September 11 to 13, the active low-pressure cell over the central South China Sea is likely to strengthen into a tropical storm. It is forecast to move close to the northern coast of Vietnam between September 13 and 14, and the public is advised to closely follow weather forecasts.
To improve safety and reduce possible impacts, the department advised people to carefully plan their daily activities and travel during the period and to continue monitoring official advisories.
Updates are available through the TMD website at www.tmd.go.th or by calling 0-2399-4012-13 or 1182, available 24 hours a day.
Provinces expected to be affected
September 11, 2026
Areas expected to receive very heavy rain
- South: Phetchaburi, Prachuap Khiri Khan and Ranong
Areas expected to receive heavy rain
- Central: Ayutthaya, Suphan Buri, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon and Samut Songkhram, including Bangkok and its vicinity
- East: Nakhon Nayok, Prachin Buri, Chachoengsao, Chon Buri, Rayong, Chanthaburi and Trat
- South: Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Pattani, Yala, Narathiwat, Phang Nga, Phuket, Krabi, Trang and Satun
September 12, 2026
Areas expected to receive very heavy rain
- South: Ranong, Phang Nga, Prachuap Khiri Khan, Chumphon and Surat Thani
Areas expected to receive heavy rain
- Northeast: Ubon Ratchathani
- Central: Nakhon Sawan, Uthai Thani, Chai Nat, Ayutthaya, Suphan Buri, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon and Samut Songkhram, including Bangkok and its vicinity
- East: Nakhon Nayok, Prachin Buri, Sa Kaeo, Chachoengsao, Chon Buri, Rayong, Chanthaburi and Trat
- South: Phetchaburi, Surat Thani, Nakhon Si Thammarat, Phatthalung, Phuket, Krabi, Trang and Satun
September 13, 2026
Areas expected to receive very heavy rain
- East: Chanthaburi and Trat
- South: Ranong and Phang Nga
Areas expected to receive heavy rain
- Northeast: Roi Et, Yasothon, Amnat Charoen, Surin, Si Sa Ket and Ubon Ratchathani
- Central: Kanchanaburi, Ratchaburi and Samut Songkhram
- East: Sa Kaeo, Chachoengsao, Chon Buri and Rayong
- South: Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat, Phuket, Krabi, Trang and Satun
