Heavy rain and flash flood warnings across North and Northeast as monsoon strengthens

Thailand’s weather is being affected by a moderate monsoon trough stretching across upper Myanmar and the upper North into a low-pressure cell over upper Laos, the Thai Meteorological Department said on Wednesday.

At the same time, a moderate southwest monsoon continues to prevail over the Andaman Sea, Thailand, and the Gulf of Thailand.

These conditions are expected to bring thundershowers and isolated heavy rainfall across much of the country, with the possibility of very heavy rain in the North and upper Northeast regions. Residents in these areas are advised to be on high alert for flash floods and run-off, especially near foothills, rivers, and low-lying areas.

At sea, waves in the upper Andaman Sea are expected to reach around 2 metres, rising above 2 metres in areas experiencing thunderstorms. In the lower Andaman Sea and the Gulf, waves are forecast at 1–2 metres, with taller waves also likely during storms.

All vessels in both seas should navigate with caution and avoid areas affected by thunderstorms, the department warned.

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

North: Fairly widespread thundershowers and isolated heavy to very heavy rain in Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Nan, Uttaradit, Phitsanulok, Phetchabun, and Tak; minimum temperature 22-25 degrees Celsius, maximum 29-33°C.

Northeast: Fairly widespread thundershowers and isolated heavy to very heavy rain in Loei, Nong Khai, Bueng Kan, Nong Bua Lamphu, Udon Thani, Sakon Nakhon, Nakhon Phanom, Kalasin, Mukdahan, Yasothon, Amnat Charoen, Sisaket and Ubon Ratchathani; minimum 22-26°C, maximum 28-31°C.

Central: Fairly widespread thundershowers and isolated heavy rain in Nakhon Sawan, Chai Nat, Sing Buri, Lop Buri, Saraburi, Kanchanaburi, Nakhon Pathom and Samut Sakhon; minimum 23-26°C, maximum 32-34°C.

East: Fairly widespread thundershowers and isolated heavy rain in Nakhon Nayok, Prachin Buri, Chachoengsao, Chonburi, Rayong, Chanthaburi and Trat; minimum 23-26°C, maximum 29-32°C; waves 1-2 metres high and above 2 metres high in thundershowers.

South (east coast): Scattered thundershowers mostly in Chumphon, Surat Thani, Nakhon Si Thammarat, Songkhla, Yala and Narathiwat; minimum 23-26°C, maximum 30-34°C; waves about a metre high and above 2 metres high in thundershowers.

South (west coast): Scattered thundershowers and isolated heavy rains in Ranong, Phang Nga and Phuket; minimum 23-26°C, maximum 27-33°C; waves 1-2 metres high and above 2 metres high in thundershowers.

Bangkok metropolitan area: Fairly widespread thundershowers with isolated heavy rain; minimum 25-27°C, maximum 31-34°C.