TMD warns of flash floods and rough seas near Phuket on 9 August

The Thai Meteorological Department (TMD) has warned of possible flash floods and runoff across Thailand as a strengthening southwest monsoon brings heavy rain and rough seas on 9 August 2026.

The forecast, covering 6am on 9 August to 6am on 10 August, predicts thunderstorms across 30% of the Andaman coast, mainly in Ranong, Phang Nga, Trang and Satun. Temperatures are expected to range from 24 to 27 degrees Celsius to 31 to 35 degrees Celsius.

From Phuket northward, southwesterly winds of 20 to 40 kilometres per hour are expected to produce waves of 2 to 3 metres. Waves could exceed 3 metres in areas affected by thunderstorms. From Krabi southward, waves are forecast to reach about 2 metres and rise higher in thunderstorms.

The TMD urged residents in areas affected by accumulated rainfall to watch for flash floods and runoff, particularly near foothills, waterways and low-lying land. Sailors were advised to exercise caution and avoid stormy areas, while small boats in the upper Andaman Sea were told to remain ashore.

The department said a monsoon trough was lying across upper northern Thailand and upper Laos, while the southwest monsoon over the Andaman Sea, Thailand and the Gulf of Thailand had strengthened.