The Thai Meteorological Department’s advisory on heavy to very heavy rain across Thailand and strong wind and waves in the Andaman Sea, effective until Monday (May 18, 2026), warns that rainfall will increase across the country, with heavy to very heavy rain in some areas of the North, Central, East and South.
People in these areas are advised to be alert to the dangers of heavy to very heavy rain and accumulated rainfall, which may cause flash floods and forest run-off, especially on foothill slopes near waterways and in low-lying areas.
This is because the southwest monsoon prevailing over the Andaman Sea, Thailand and the Gulf of Thailand is becoming stronger.
People are also advised to take care of their health during changing weather conditions.
Wind and waves in the Andaman Sea and the Gulf of Thailand are also becoming stronger.
In the upper Andaman Sea, from Phuket province northwards, waves are 2-3 metres high and more than 3 metres in thundershowers.
In the lower Andaman Sea, from Krabi province southwards, and the upper Gulf of Thailand, waves are about 2 metres high and more than 2 metres in thundershowers.
Mariners in these areas should navigate with caution and avoid thundershower areas, while small boats in the upper Andaman Sea should remain ashore.
Issued on Friday (May 15, 2026) at 5pm.
