Thailand warns 4 provinces of very heavy rain on Sept 12
Bangkok and surrounding areas face 70% thunderstorm coverage on September 12, with warnings of flash floods, runoff and landslides
- The Thai Meteorological Department (TMD) forecasts isolated very heavy rain in Prachuap Khiri Khan, Chumphon, Ranong and Phang Nga during the 24 hours from 6am on September 12, Thai time.
- The TMD forecasts thunderstorms over 70% of the Central region, East, both southern coasts, and Bangkok and surrounding areas in its September 12 forecast.
- Heavy and accumulated rain could cause flash floods, rapid runoff and landslides, particularly near foothill waterways and in low-lying areas, the TMD warned.
- A low-pressure system off central Vietnam is likely to become a tropical cyclone on September 12–13 and approach northern Vietnam’s coast on September 13–14, according to the TMD.
The Thai Meteorological Department (TMD) warned of isolated very heavy rain in four southern provinces on Saturday (September 12, 2026), with heavy rain also forecast in Bangkok and several other regions. The 24-hour outlook covers 6am on September 12 to 6am on September 13, Thai time (UTC+7).
Prachuap Khiri Khan, Chumphon, Ranong and Phang Nga could see very heavy downpours as rainfall increases across the South, according to the TMD. Isolated heavy rain is also forecast in the lower Northeast, the Central region including Bangkok and surrounding areas, and the East.
Heavy rain raises flood and landslide risks in Thailand
The TMD warned that heavy and accumulated rainfall could trigger flash floods and rapid runoff, as well as landslides, especially on foothill slopes near waterways and in low-lying areas.
Residents in areas covered by the TMD warning should avoid routes repeatedly affected by flooding, particularly low-lying roads where water could accumulate temporarily.
The TMD described winds and waves in the Andaman Sea and Gulf of Thailand as moderate and urged mariners to navigate cautiously and avoid thunderstorms. Waves in the upper Andaman Sea are forecast at about 2 metres, exceeding 2 metres in thunderstorms.
Vietnam coastal low could become a tropical cyclone
A strong low-pressure area off central Vietnam is likely to strengthen into a tropical cyclone during September 12–13, the TMD said. The system is expected to approach the coast of northern Vietnam during September 13–14, and the public should continue following weather forecasts.
The TMD attributed Thailand’s wet weather to a high-pressure system, or cool air mass, extending over the upper North and upper Northeast, while a monsoon trough crosses the lower Central region, upper South, upper Gulf of Thailand and East towards the strong low off central Vietnam. A moderate southwest monsoon also covers the Andaman Sea, southern Thailand and the Gulf of Thailand.
Storm coverage reaches 70% in several Thai regions
The TMD forecasts thunderstorms over 70% of the Central region, East, both southern coasts, and Bangkok and surrounding areas during the 24 hours from 6am on September 12. The regional details below apply until 6am on September 13.
North: The TMD’s September 12 forecast puts thunderstorm coverage at 40%, mainly in Mae Hong Son, Chiang Mai, Tak, Phichit, Kamphaeng Phet and Phetchabun. Minimum temperatures are 21–26°C and maximum temperatures 31–36°C. Easterly winds are forecast at 10–20 km/h.
Northeast: Thunderstorms are forecast over 40% of the region, with isolated heavy rain in Ubon Ratchathani, according to the TMD’s September 12 outlook. Minimum temperatures are 21–24°C and maximum temperatures 33–34°C. Northeasterly winds are expected at 10–20 km/h.
Central region: The TMD’s September 12 forecast gives 70% thunderstorm coverage, with isolated heavy rain in Nakhon Sawan, Uthai Thani, Chai Nat, Phra Nakhon Si Ayutthaya, Suphan Buri, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon and Samut Songkhram. Minimum temperatures are 23–25°C and maximum temperatures 33–35°C. Northerly winds are forecast at 10–20 km/h.
East: Thunderstorms are expected over 70% of the region, with isolated heavy rain in Nakhon Nayok, Prachin Buri, Sa Kaeo, Chachoengsao, Chon Buri, Rayong, Chanthaburi and Trat, according to the TMD’s September 12 forecast. Minimum temperatures are 23–25°C and maximum temperatures 31–34°C, with variable winds at 15–35 km/h. Waves are forecast at 1–2 metres, exceeding 3 metres in thunderstorms.
South, east coast: The TMD’s September 12 forecast gives 70% thunderstorm coverage, with isolated heavy rain in Phetchaburi, Surat Thani, Nakhon Si Thammarat and Phatthalung, and isolated very heavy rain in Prachuap Khiri Khan and Chumphon. Minimum temperatures are 22–24°C and maximum temperatures 31–33°C. From Surat Thani northwards, westerly winds will reach 15–35 km/h, with waves of 1–2 metres and more than 2 metres in thunderstorms; from Nakhon Si Thammarat southwards, northwesterly winds will reach 15–35 km/h, with waves of about 1 metre, rising to 1–2 metres offshore and more than 2 metres in thunderstorms.
South, west coast: Thunderstorms are forecast over 70% of the region, with isolated heavy rain in Phuket, Krabi, Trang and Satun, and isolated very heavy rain in Ranong and Phang Nga, according to the TMD’s September 12 outlook. Minimum temperatures are 23–25°C and maximum temperatures 29–32°C. From Phuket northwards, westerly winds will reach 20–35 km/h, with waves of about 2 metres and more than 2 metres in thunderstorms; from Krabi southwards, northwesterly winds will reach 15–35 km/h, with waves of 1–2 metres and more than 2 metres in thunderstorms.
Bangkok and surrounding areas: The TMD’s September 12 forecast puts thunderstorm coverage at 70%, with isolated heavy rain. Minimum temperatures are 24–25°C and maximum temperatures 33–34°C. Northwesterly winds are expected at 10–20 km/h.
