Heavy rain forecast for much of Thailand, warnings for flash floods and rough seas

The Thai Meteorological Department has forecast increased rainfall for Saturday (August 16), with widespread showers and isolated heavy to very heavy rain in some areas, particularly in the East and along the western coast of the South.

Residents in Phitsanulok, Phetchabun, Chanthaburi, Trat, Ranong, and Phang Nga are advised to be on high alert for heavy to very heavy rain and accumulated rainfall, which may trigger flash floods and run-off, especially in foothill areas, near waterways, and low-lying zones.

The weather conditions are being driven by a monsoon trough across the North and Northeast, combined with a strengthening south-westerly monsoon covering the Andaman Sea, Thailand, and the Gulf of Thailand, while a low-pressure cell is forming over the lower North.

In the upper Andaman Sea, waves will reach 2–3 metres, rising above 3 metres in stormy areas. The lower Andaman Sea and the upper Gulf of Thailand will see waves around 2 metres, rising above 2 metres in thunderstorms. 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.

The weather forecast for the next 24 hours is as follows:

North: Fairly widespread thundershowers and isolated heavy to very heavy rains in Mae Hong Son, Chiang Mai, Chiang Rai, Lamphun, Lampang, Phayao, Nan, Phrae, Uttaradit, Sukhothai, Tak, Kamphaeng Phet, Phitsanulok, Phichit and Phetchabun; minimum temperature 22-25 degrees Celsius, maximum 30-33°C. 

Northeast: Fairly widespread thundershowers and isolated heavy rains in Loei, Nong Khai, Bueng Kan, Nong Bua Lamphu, Chaiyaphum, Khon Kaen, Maha Sarakham, Nakhon Ratchasima, Buriram, Surin, Sisaket and Ubon Ratchathani; minimum 22-24°C, maximum 30-32°C.

Central: Fairly widespread thundershowers and isolated heavy rains in Nakhon Sawan, Uthai Thani, Chainat, Lopburi, Saraburi and Kanchanaburi; minimum 23-25°C, maximum 31-34°C. 

East: Fairly widespread thundershowers and isolated heavy to very heavy rains in Nakhon Nayok, Prachinburi, Sa Kaeo, Chachoengsao, Chonburi, Rayong, Chanthaburi and Trat; minimum 23-26°C, maximum 28-32°C; waves about 2 metres high and above 2 metres high in thundershowers.

South (east coast): Scattered thundershowers and isolated heavy rains in Prachuap Khiri Khan, Chumphon and Surat Thani; minimum 23-25°C, maximum 30-33°C; waves about 1-2 metres high and above 2 metres high in thundershowers.

South (west coast): Fairly widespread thundershowers and isolated heavy to very heavy rains in Ranong, Phang Nga, Phuket and Krabi; minimum 23-25°C, maximum 28-31°C; waves about 2 metres high and above 2 metres high in thundershowers.

Bangkok metropolitan area: Fairly widespread thundershowers and isolated heavy rains; minimum 25-27°C, maximum 31-33°C.