TMD warns of heavy rain, 2–3m Andaman waves for Sept 17–20
Heavy rain is forecast in Thailand’s North and Northeast from September 17, spreading to the Central region, East and South on September 18
The Thai Meteorological Department (TMD) issued its third warning on September 16, 2026, forecasting heavy to very heavy rain in parts of Thailand and strong winds and waves in the Andaman Sea from September 17–20. Bulletin No. 3 (207/2569) was issued at 5am Thai time (UTC+7).
North and Northeast face heavy rain first
The TMD expects the North and Northeast to be affected first on September 17. The Central region, East and South will be affected the following day, September 18, during the September 17–20 heavy-rain and rough-sea warning period.
The TMD attributed the changing weather to a high-pressure system, or cool air mass, from China that will extend over the upper North and upper Northeast. The system will push the monsoon trough southwards across the lower Central region, East and upper South.
The southwest monsoon over the Andaman Sea, Thailand and the Gulf of Thailand will also strengthen, according to the TMD.
The TMD warned that heavy to very heavy rain and accumulated rainfall could trigger flash floods and forest runoff, particularly on foothill slopes near waterways and in low-lying areas.
People should avoid routes prone to repeated flooding, especially low-lying roads where temporary waterlogging may occur, the TMD advised. The department also urged the public to plan daily activities and travel carefully during September 17–20 to reduce risks and potential disruption.
Andaman waves forecast at 2–3 metres
The TMD expects fairly strong winds over the Andaman Sea, with waves 2–3 metres high and more than three metres in thunderstorms.
Mariners in both the Gulf of Thailand and the Andaman Sea should navigate cautiously and avoid thunderstorms, the TMD advised. Small boats in the Andaman Sea should remain ashore from September 17–20.
Next TMD bulletin scheduled for September 16 at 5pm
The TMD scheduled its next warning for 5pm Thai time on September 16 and urged the public to follow further announcements.
Weather information is available around the clock through the Thai Meteorological Department website or by calling 02-399-4012, 02-399-4013 or 1182.
