Thailand Braces for Heavy Rain, Flash Floods Through September 20
Thailand's Meteorological Department warns of heavy to very heavy rain and flash floods across the country through September 20, with southern regions like Ranong, Phang Nga, and Phuket facing the most severe conditions.
The Meteorological Department issued its second warning on September 15 concerning heavy to very heavy rainfall across Thailand and strong winds in the Andaman Sea from September 17–20, 2025. The rain is expected to begin in the northern and northeastern regions on September 17, spreading to central, eastern, and southern areas by September 18. The system is being driven by a high-pressure zone and cool air mass from China moving south, which will push a monsoon trough downward across the lower central, eastern, and upper southern regions, combined with an intensifying southwestern monsoon over the Andaman Sea, Thailand, and the Gulf of Thailand.
Authorities warn the public to stay alert for dangers from heavy rainfall and accumulated moisture, which could trigger flash floods and forest flooding. Residents near waterways, hillsides, and low-lying areas should avoid routes prone to recurring floods and take extra care in areas at risk of temporary inundation. The Andaman Sea is forecast to see moderate to strong winds with wave heights of 2–3 meters, rising above 3 meters in thunderstorm areas. Fishermen in the Gulf of Thailand and Andaman Sea should navigate cautiously and avoid storm zones. Small boats in the Andaman Sea should remain ashore from September 17–20.
The public is urged to plan activities and travel carefully during this period and monitor updates from the Meteorological Department via its website at http://www.tmd.go.th or by calling 0-2399-4012-13 and 1182, available 24 hours.
Provincial Risk Assessment:
September 17 – Very Heavy Rain: Uttaradit, Phichit, Phitsanulok, Phetchabun (northern); Loei (northeastern); Ranong, Phang Nga (southern).
September 17 – Heavy Rain: Chiang Mai, Chiang Rai, Lampun, Lamphun, Phayao, Nan, Phrae, Sukhothai, Kamphaeng Phet (northern); Nong Khai, Bueng Kan, Nong Bua Lamphu, Udon Thani, Sakon Nakhon, Nakhon Phanom, Kalasin, Mukdahan, Khon Kaen, Maha Sarakham, Roi Et, Yasothon, Amnat Charoen, Chaiyaphum, Nakhon Ratchasima, Buriram, Surin, Si Sa Ket, Ubon Ratchathani (northeastern); Nakhon Sawan, Saraburi (central); Nakhon Nayok, Prachuap Khiri Khan, Sa Kaeo, Chachoengsao, Chonburi, Rayong, Chanthaburi, Trat (eastern); Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Phuket, Krabi, Trang, Satun (southern).
September 18 – Very Heavy Rain: Ranong, Phang Nga, Phuket, Chumphon, Surat Thani (southern).
September 18 – Heavy Rain: Mae Hong Son, Chiang Mai, Lampun, Lamphun, Phayao, Nan, Phrae, Uttaradit, Sukhothai, Kamphaeng Phet, Phichit, Phitsanulok, Phetchabun, Tak (northern); Loei, Nong Bua Lamphu, Udon Thani, Kalasin, Khon Kaen, Maha Sarakham, Roi Et, Yasothon, Amnat Charoen, Chaiyaphum, Nakhon Ratchasima (northeastern).
