Heavy rain puts Thailand’s North and Northeast on flash-flood alert
The Thai Meteorological Department warns of flash floods from heavy to very heavy rain and advises small boats in the Andaman Sea to stay ashore until Sunday.
- The Thai Meteorological Department has issued a warning for heavy to very heavy rain across Thailand from September 17-20, 2026.
- The North and Northeast regions are expected to be the first areas affected by the severe weather.
- Residents are alerted to the danger of flash floods and rapid run-off, especially in low-lying areas and near waterways.
- The weather system is also forecast to bring strong winds and waves up to 3 meters in the Andaman Sea, with a warning for small boats to stay ashore.
The Thai Meteorological Department (TMD) issued a warning at 5pm on Thursday covering September 17-20, 2026, forecasting heavy to very heavy rain across Thailand and strong winds and waves in the Andaman Sea.
The North and Northeast are expected to be affected first on Thursday, followed by the Central, Eastern and Southern regions on Friday.
A high-pressure system or cold air mass from China is forecast to extend over the upper North and upper Northeast, causing the monsoon trough to shift southwards and lie across the lower Central region, the East and the upper South.
The southwest monsoon prevailing over the Andaman Sea, Thailand and the Gulf of Thailand is also expected to strengthen.
“People across Thailand should be alert to dangers from heavy to very heavy rain and accumulated rainfall, which could cause flash floods and rapid run-off from higher ground, particularly on foothill slopes near waterways and in low-lying areas. They should avoid travelling along routes repeatedly affected by flooding, especially through low-lying areas where temporary inundation may occur.”
Small boats advised to stay ashore as Andaman Sea waves may reach 3 metres
Wind-waves in the Andaman Sea are expected to be fairly strong, with waves 2-3 metres high and rising above 3 metres in areas with thunderstorms.
Mariners in the Gulf of Thailand and the Andaman Sea should navigate with caution and avoid sailing in areas with thunderstorms.
Small boats in the Andaman Sea should remain ashore throughout the period.
For safety and to minimise possible impacts, the public should plan daily activities and travel carefully during the period.
People are also advised to follow TMD announcements and updates at www.tmd.go.th or by calling 0-2399-4012-13 or 1182.
Information is available through these channels 24 hours a day.
