BANGKOK — 11 June 2026, Thailand’s Meteorological Department has warned of increased rainfall and possible flash flooding across much of the country, with heavy to very heavy rain forecast for 63 provinces as monsoon conditions intensify.
In its 24-hour forecast issued on 11 June 2026, the department said northern Thailand, the upper Northeast, the East and the Andaman coast in the South were expected to experience the heaviest rainfall.
The weather conditions are being driven by a monsoon trough stretching across Myanmar and northern Thailand into a low-pressure area over the northern South China Sea. A moderate south-westerly monsoon continues to prevail over the Andaman Sea, Thailand and the Gulf of Thailand.
Authorities urged residents in affected areas to remain alert for heavy and accumulated rainfall, warning of possible flash floods and forest run-off, particularly in low-lying areas and locations near waterways.
Moderate seas are expected in the upper Andaman Sea, where waves could reach about 2 metres. Waves in the lower Andaman Sea and the Gulf of Thailand are forecast at 1 to 2 metres, rising above 2 metres during thunderstorms. Mariners have been advised to exercise caution and avoid sailing in storm-affected areas.
The forecast covers the period from 06:00 on 11 June to 06:00 on 12 June.
In the North, thunderstorms are expected across 70% of the region, with heavy to very heavy rain forecast in Mae Hong Son, Chiang Mai, Chiang Rai, Lamphun, Lampang, Phayao, Nan, Phrae, Uttaradit, Kamphaeng Phet, Phichit, Sukhothai, Phitsanulok, Phetchabun and Tak.
The Northeast is also expected to see thunderstorms across 70% of the region, with heavy to very heavy rain likely in Loei, Nong Bua Lamphu, Nong Khai, Bueng Kan, Udon Thani, Sakon Nakhon, Nakhon Phanom, Chaiyaphum, Khon Kaen, Kalasin, Mukdahan, Maha Sarakham, Roi Et, Yasothon, Amnat Charoen, Ubon Ratchathani, Nakhon Ratchasima, Buri Ram, Surin and Si Sa Ket.
In the Central Plains, thunderstorms are forecast across 60% of the area, with heavy rain expected in Nakhon Sawan, Uthai Thani, Chai Nat, Lop Buri, Saraburi, Kanchanaburi, Ratchaburi, Nakhon Pathom and Samut Sakhon.
The eastern region is forecast to experience thunderstorms over 60% of the area, with heavy to very heavy rain in Nakhon Nayok, Prachin Buri, Sa Kaeo, Rayong, Chanthaburi and Trat.
Along the eastern coast of southern Thailand, thunderstorms are expected across 40% of the region, mainly in Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung and Songkhla.
The western coast of the South is expected to face the most severe conditions, with thunderstorms forecast across 80% of the region and heavy to very heavy rain likely in Ranong, Phang Nga, Phuket, Krabi, Trang and Satun.
Bangkok and surrounding provinces are forecast to experience thunderstorms across 60% of the metropolitan area, with isolated heavy rain possible.
Temperatures nationwide are expected to range from 23C to 36C. Authorities continue to advise residents in flood-prone areas to monitor weather updates closely and prepare for possible weather-related emergencies.
