Heavy rain and flash flood warning as monsoon strengthens across Thailand

People in affected areas are urged to beware of heavy rainfall and water accumulation that may cause flash floods and overflows.

The Thai Meteorological Department has issued a weather alert on Thursday as the southwest monsoon continues to prevail over the Andaman Sea, Thailand, and the Gulf of Thailand, bringing widespread thundershowers and isolated heavy rain to parts of the East, the South (west coast), and the Bangkok metropolitan area.

Residents in these areas are advised to exercise caution due to the risk of heavy rainfall, which may lead to flash floods and water accumulation, particularly near foothills, waterways, and low-lying areas, the department said.

In the South, waves in the Andaman Sea are expected to reach about 1 metre high, below 1 metre in the Gulf, and above 2 metres in areas with thundershowers. All ships should proceed with caution and avoid thundershowers, the department warned.The department added that from May 23-27, the southwest monsoon prevailing over the Andaman Sea, Thailand, and the Gulf is expected to strengthen, while the monsoon trough will lie across the upper country and the upper South. More rains and isolated heavy to very heavy rainfall are likely throughout Thailand during this period.

Residents should remain vigilant for potential flash floods and overflows, particularly along waterways near foothills and low-lying areas. Due to variable weather, people are advised to maintain good health, and farmers are urged to take preventive measures to protect their crops from damage, the department said.

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

North: Scattered thundershowers mostly in Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Nan, Lampang, Phichit, Sukhothai, Uttaradit, Phitsanulok, and Phetchabun; minimum temperature 23-27 degrees Celsius, maximum 33-37°C. 

Northeast: Scattered thundershowers mostly in Loei, Nong Khai, Bueng Kan, Udon Thani, Sakon Nakhon, Nakhon Phanom, Chaiyaphum, Nakhon Ratchasima and Ubon Ratchathani; minimum 23-25°C, maximum 33-35°C.

Central: Scattered thundershowers mostly in Nakhon Sawan, Uthai Thani, Lopburi, Saraburi, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon, and Samut Songkhram; minimum 24-26°C, maximum 35-37°C. 

East: Scattered thundershowers and isolated heavy rains in Nakhon Nayok, Chachoengsao, Chonburi, Rayong, Chanthaburi and Trat; minimum 25-27°C, maximum 32-34°C; waves below a metre high and above 2 metres high in thundershowers.

South (east coast): Scattered thundershowers mostly in Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani and Nakhon Si Thammarat; minimum 24-26°C, maximum 32-35°C; waves below a metre high and above 2 metres high in thundershowers.

South (west coast): Scattered thundershowers and isolated heavy rains in Ranong, Phang Nga, Phuket, Krabi and Trang; minimum 24-26°C, maximum 31-33°C; waves about a metre high and above 2 metres high in thundershowers.

Bangkok metropolitan area: Scattered thundershowers and isolated heavy rains; minimum 25-27°C, maximum 31-34°C.

(2025/05/22-00:00)