TMD warns of heavy rain, 2–3m upper Gulf waves on Sept 23–27
Thailand’s lower Northeast and East face heavy rain first, while small boats in the upper Gulf are advised to stay ashore on September 24–27
- The Thai Meteorological Department forecasts heavy to very heavy rain across multiple regions of Thailand from September 23–27, bringing risks of flash floods.
- Waves in the upper Gulf of Thailand are expected to reach 2–3 meters high, and may exceed 3 meters during thunderstorms.
- Due to the rough sea conditions, small boats in the upper Gulf are advised to remain ashore from September 24–27.
The Thai Meteorological Department (TMD) warned on Wednesday (September 23, 2026) that heavy to very heavy rain would affect several regions of Thailand from September 23–27, bringing risks of flash floods and forest run-off.
Lower Northeast and East face heavy rain first
The lower Northeast and East will be affected first, before the rain spreads to other regions. The areas covered by the September 23–27 rain forecast also include the North, Central region, including Bangkok and surrounding provinces, and South, with heavy rain in many places and very heavy rain in some areas.
The TMD attributed the wet spell to a strong low-pressure system near the central Vietnamese coast, which is expected to move over the lower Northeast, East and Central region, including Bangkok and surrounding provinces, along the monsoon trough across upper Thailand.
The southwest monsoon over the Andaman Sea, Thailand and the Gulf of Thailand will strengthen at the same time.
TMD warns of flash floods near hills and waterways
The TMD warned that continued heavy to very heavy rain and accumulated rainfall could cause flash floods and forest run-off, particularly on foothill slopes near waterways and in low-lying areas.
The TMD advised travellers to avoid routes with recurring flooding, especially low-lying roads where water could accumulate temporarily. Residents were also urged by the TMD to plan daily activities and journeys carefully during September 23–27 to reduce potential disruption and stay safe.
Upper Gulf waves forecast to reach 2–3 metres
The TMD forecast stronger winds and rougher seas in the Andaman Sea and Gulf of Thailand, with waves of 2–3 metres in the upper Gulf and more than 3 metres in thunderstorms.
Waves in the lower Gulf and upper Andaman Sea are forecast to reach around 2 metres, exceeding 2 metres in thunderstorms.
The TMD advised mariners throughout the Gulf and Andaman Sea to proceed cautiously and avoid thunderstorms. Small boats in the upper Gulf should remain ashore from September 24–27.
The TMD urged the public to follow official announcements and said weather information was available around the clock through its website and telephone numbers 02-399-4012, 02-399-4013 and 1182.
The TMD will issue its next warning at 5pm Thailand time on September 23.
