Intense rainfall anticipated across Thailand, advisories issued for potential flash flooding and treacherous sea conditions
Heavy Rain and Flash Flood Warnings Across Thailand
The Thai Meteorological Department has issued warnings for heavy rain and flash flood risks across several provinces in Thailand from August 16 to 27, 2025.
August 16: Heavy rains with flash flood risks are expected in six provinces: Phitsanulok, Phetchabun, Chanthaburi, Trat, Ranong, and Phang Nga. This is due to a monsoon trough and strengthening southwest monsoon affecting the Andaman Sea, Thailand, and the Gulf of Thailand, producing isolated very heavy rain and risks of run-off and flash floods especially in foothill areas, waterways, and low-lying zones [3].
August 17 and following days up to August 27: Continued risks of heavy to very heavy rain and flash floods are expected in the North, upper Northeast, Central, Eastern regions, including Bangkok. These conditions are due to a tropical depression over the Philippines moving west-northwest, intensifying, and strengthening the southwest monsoon [1].
Marine conditions: High waves and rough seas are expected in the Andaman Sea and Gulf of Thailand, with advisories for ships and small boats to exercise caution or remain ashore [3][1].
Regional Weather Conditions
- Northeast: Fairly widespread thundershowers and isolated heavy to very heavy rains are expected in Loei, Nong Khai, Bueng Kan, Nong Bua Lamphu, Chaiyaphum, Khon Kaen, Maha Sarakham, Nakhon Ratchasima, Buriram, Surin, Sisaket, and Ubon Ratchathani. The temperature range will be 22-24°C to 30-32°C [1].
- East: Fairly widespread thundershowers and isolated heavy to very heavy rains are expected in Nakhon Nayok, Prachinburi, Sa Kaeo, Chachoengsao, Chonburi, Rayong, Chanthaburi, and Trat. The temperature range will be 23-26°C to 28-32°C, and waves about 2 metres high and above 2 metres high in thundershowers [1].
- South (east coast): Scattered thundershowers and isolated heavy rains are expected in Prachuap Khiri Khan, Chumphon, and Surat Thani. The temperature range will be 23-25°C to 30-33°C, and waves about 1-2 metres high and above 2 metres high in thundershowers [1].
- South (west coast): Fairly widespread thundershowers and isolated heavy to very heavy rains are expected in Ranong, Phang Nga, Phuket, and Krabi. The temperature range will be 23-25°C to 28-31°C, and waves about 2 metres high and above 2 metres high in thundershowers [1].
- Central: Fairly widespread thundershowers and isolated heavy rains are expected in Nakhon Sawan, Uthai Thani, Chainat, Lopburi, Saraburi, and Kanchanaburi. The temperature range will be 23-25°C to 31-34°C [1].
Waves in the Andaman Sea and Gulf of Thailand
Waves in the upper Andaman Sea will reach 2-3 metres, rising above 3 metres in stormy areas, while the lower Andaman Sea and the upper Gulf of Thailand will see waves around 2 metres, rising above 2 metres in thunderstorms [1].
Preparations and Advisories
The NWRO has prepared for Sirikit Dam discharge and Chao Phraya floodplain storage as heavy rain hits mid-August. Residents in the aforementioned provinces are advised to be on high alert for heavy to very heavy rain and accumulated rainfall [2].
Mariners are urged to proceed with caution, avoid sailing in stormy areas, and for small boats in the upper Andaman Sea to remain ashore until August 17 [3][1].
A low-pressure cell is forming over the lower North [3].
Sources
[1] The Thai Meteorological Department's forecast for August 16-27, 2025.
[2] NWRO's preparations for Sirikit Dam discharge and Chao Phraya floodplain storage as heavy rain hits mid-August.
[3] The Thai Meteorological Department's warning on August 15, 2025, of heavy rain expected on August 16, with flash flood risks in six provinces: Phitsanulok, Phetchabun, Chanthaburi, Trat, Ranong, and Phang Nga.
Businesses in the affected provinces (Phitsanulok, Phetchabun, Chanthaburi, Trat, Ranong, and Phang Nga) should prepare for potential disruptions due to the heavy rain and flash flood risks. High alert and proper precautions should be taken by businesses operating in North, upper Northeast, Central, Eastern regions, including Bangkok, due to the continued risks of heavy to very heavy rain and flash floods from August 17 to 27.
