Heavy rain and possible flash floods forecast across four Thai regions
The Thai Meteorological Department forecasts isolated heavy rain in four regions, while small boats in the upper Andaman Sea are advised to remain ashore.
- The Thai Meteorological Department has forecast isolated heavy rain across four regions: the North, upper Northeast, Central, and East.
- This rainfall creates a risk of flash floods and forest run-off, particularly in low-lying areas and on foothill slopes near waterways.
- The weather system is also causing rough seas in the upper Andaman Sea, with waves reaching 2-3 meters, and small boats are advised to remain ashore.
The Thai Meteorological Department (TMD) forecast that isolated heavy rain would continue in the North, upper Northeast, Central and East over the following 24 hours.
The forecast was issued at 5pm on Thursday (August 13, 2026).
The conditions were attributed to a monsoon trough stretching across Myanmar, upper Laos and upper Vietnam, together with a rather strong southwest monsoon covering the Andaman Sea, Thailand and the Gulf of Thailand.
Heavy rain and accumulated rainfall could cause flash floods and forest run-off, particularly on foothill slopes close to waterways and in low-lying areas.
Rivers could also overflow their banks in the Northeast.
Conditions in the upper Andaman Sea will be rather rough, with waves 2–3 metres high and above 3 metres during thundershowers.
Mariners are advised to exercise caution and avoid areas with thundershowers, while small boats in the upper Andaman Sea should remain ashore.
Heavy-rain risk areas from 6pm Thursday (August 13) to 6pm Friday (August 14)
North
- Thundershowers are forecast across 60% of the region.
- Isolated heavy rain is expected in Mae Hong Son, Nan and Tak.
- Minimum temperatures will be 23 to 27°C.
- Maximum temperatures will be 32 to 35°C.
- Southwesterly winds will reach 10 to 20 km/h.
Northeast
- Thundershowers are forecast across 60% of the region.
- Isolated heavy rain is expected in Bueng Kan, Sakon Nakhon, Nakhon Phanom and Mukdahan.
- Minimum temperatures will be 24 to 26°C.
- Maximum temperatures will be 33 to 35°C.
- Southwesterly winds will reach 10 to 20 km/h.
Central region
- Thundershowers are forecast across 40% of the region.
- Isolated heavy rain is expected in Saraburi and Kanchanaburi.
- Minimum temperatures will be 24 to 27°C.
- Maximum temperatures will be 33 to 35°C.
- Southwesterly winds will reach 10 to 25 km/h.
East
- Thundershowers are forecast across 60% of the region.
- Isolated heavy rain is expected in Nakhon Nayok, Prachin Buri, Chanthaburi and Trat.
- Minimum temperatures will be 24 to 28°C.
- Maximum temperatures will be 31 to 35°C.
- Southwesterly winds will reach 20 to 35 km/h.
- Waves will be around 2 metres high.
- Waves may exceed 2 metres during thundershowers.
Southern east coast
- Thundershowers are forecast across 40% of the region.
- Rain is expected mainly in Chumphon, Surat Thani and Nakhon Si Thammarat.
- Minimum temperatures will be 23 to 26°C.
- Maximum temperatures will be 33 to 36°C.
- Southwesterly winds will reach 20 to 35 km/h.
- Waves will be 1 to 2 metres high.
- Offshore waves will be around 2 metres high.
- Waves may exceed 2 metres during thundershowers.
Southern west coast
- Thundershowers are forecast across 60% of the region.
- Rain is expected mainly in Ranong, Phang Nga and Phuket.
- Minimum temperatures will be 23 to 26°C.
- Maximum temperatures will be 32 to 35°C.
- From Phang Nga northwards, southwesterly winds will reach 20 to 40 km/h. Waves will be 2 to 3 metres high and may exceed 3 metres during thundershowers.
- From Phuket southwards, southwesterly winds will reach 15 to 35 km/h. Waves will be 1 to 2 metres high and may exceed 2 metres during thundershowers.
Bangkok and vicinity
- Thundershowers are forecast across 60% of the area.
- Isolated heavy rain is expected.
- Minimum temperatures will be 26 to 27°C.
- Maximum temperatures will be 34 to 35°C.
- Southwesterly winds will reach 10 to 25 km/h.
