Flash-flood, heavy rain warning issued across upper Thailand
TMD warns of flash floods and landslides, with waves above three metres in storms and small boats told to stay ashore.
The Thai Meteorological Department (TMD) has warned of heavy to very heavy rain across upper Thailand, with accumulated rainfall posing risks of flash floods, overflowing waterways and landslides.
Weather Advisory No. 11 (178/2026), issued at 5pm on Monday (August 31, 2026), forecast increased rainfall across the country, particularly in western areas of the North and Central regions, the upper and eastern parts of the Northeast, and the East.
The conditions are being driven by a monsoon trough moving across the North and upper Northeast and extending into a tropical depression over southern coastal China. A rather strong southwest monsoon is also prevailing over the Andaman Sea, Thailand and the Gulf of Thailand.
Flash floods and landslides threaten vulnerable areas
People in affected areas were advised to remain alert for heavy and very heavy rain and the effects of accumulated rainfall.
The department warned that intense downpours could cause flash floods, overflowing waterways and landslides, particularly in communities along watercourses, near foothills and in low-lying areas.
Residents should closely monitor weather forecasts and official warnings as the monsoon conditions bring more widespread rain.
Small boats told to remain ashore
The rather strong southwest monsoon is also generating rough conditions in the Andaman Sea and the Gulf of Thailand.
Waves in the upper Andaman Sea and upper Gulf are forecast to reach two to three metres, rising above three metres in thunderstorms.
In the lower Andaman Sea, waves are expected to be about two metres high and exceed two metres during thunderstorms.
All vessels in the Andaman Sea and Gulf of Thailand should proceed with caution and avoid thunderstorms. Small boats in the upper Andaman Sea and upper Gulf should remain ashore.
Depression forecast to move near Taiwan
The tropical depression over southern China is expected to intensify and move near Taiwan from September 3-4, 2026.
Passengers were advised to check the latest weather information before departure. The system is not forecast to move towards Thailand.
The advisory was signed by TMD Director-General Sugunyanee Yavinchan. The department is scheduled to issue its next update at 5am on Tuesday (September 1, 2026).
