Thailand faces more rain, flood risk, forest run-off and rough seas
The Thai Meteorological Department says rainfall will increase across several regions, with small boats urged to stay ashore in the upper Andaman Sea.
- A strengthening southwest monsoon is causing increased rainfall across Thailand, with heavy to very heavy rain forecast for the North, Central, East, and South.
- Authorities warn of a high risk of flash floods and forest run-off, especially in low-lying areas and on foothill slopes near waterways.
- The Andaman Sea and Gulf of Thailand are experiencing stronger winds and rough seas, with waves reaching 2-3 meters or more, prompting a warning for small boats to stay ashore.
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.
Thai Meteorological Department 24-hour forecast
The Thai Meteorological Department’s forecast for the next 24 hours says Thailand will see more rain and heavy rain in some areas, with very heavy rain in some parts of the North, Central and East.
This is because the southwest monsoon prevailing over the Andaman Sea, Thailand and the Gulf of Thailand is expected to strengthen.
People are advised to be alert to thundershowers, 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.
They are also advised to take care of their health during changing weather conditions.
Wind and waves in the upper Andaman Sea are strengthening.
Waves in the upper Andaman Sea are 2-3 metres high and more than 3 metres in thundershowers.
In the lower Andaman Sea and the upper Gulf of Thailand, waves are 1-2 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.
Weather forecast for Thailand from 6pm on Friday (May 15, 2026) to 6pm on Saturday (May 16, 2026)
The North
- Thundershowers are expected in 70% of the area, with heavy rain in many areas and very heavy rain in some places in Mae Hong Son, Chiang Mai, Chiang Rai, Lamphun, Lampang, Tak and Kamphaeng Phet. Minimum temperatures 22-26 degrees Celsius; maximum temperatures 29-34 degrees Celsius. Southwesterly winds 10-20 km/h.
The Northeast
- Thundershowers are expected in 60% of the area, with heavy rain in many areas in Loei, Sakon Nakhon, Nakhon Phanom, Chaiyaphum, Kalasin, Mukdahan, Yasothon, Amnat Charoen and Ubon Ratchathani. Minimum temperatures 24-27 degrees Celsius; maximum temperatures 35-37 degrees Celsius. Southwesterly winds 10-20 km/h.
The Central region
- Thundershowers are expected in 60% of the area, with heavy rain and very heavy rain in some places in Nakhon Sawan, Uthai Thani, Kanchanaburi, Nakhon Pathom and Ratchaburi. Minimum temperatures 24-27 degrees Celsius; maximum temperatures 35-36 degrees Celsius. Southwesterly winds 10-20 km/h.
The East
- Thundershowers are expected in 60% of the area, with heavy rain and very heavy rain in some places in Chanthaburi and Trat. Minimum temperatures 25-27 degrees Celsius; maximum temperatures 32-35 degrees Celsius. Southwesterly winds 15-35 km/h. Waves 1-2 metres high and more than 2 metres in thundershowers.
The South East Coast
- Thundershowers are expected in 60% of the area, with heavy rain in some places in Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat, Songkhla, Pattani, Yala and Narathiwat. Minimum temperatures 23-26 degrees Celsius; maximum temperatures 33-35 degrees Celsius. Southwesterly winds 15-30 km/h. Waves about 1 metre high and more than 2 metres in the thundershowers.
The South, the West Coast
- Thundershowers are expected in 70% of the area, with heavy rain in some places in Ranong, Phang Nga, Trang and Satun. Minimum temperatures 23-26 degrees Celsius; maximum temperatures 32-34 degrees Celsius.
- From Phang Nga province northwards: Southwesterly winds 20-40 km/h. Waves 2-3 metres high and more than 3 metres in thundershowers.
- From Phuket province southwards: Southwesterly winds 15-35 km/h. Waves 1-2 metres high and more than 2 metres in thundershowers.
Bangkok and the surrounding provinces
- Thundershowers are expected in 60% of the area. Minimum temperatures 25-27 degrees Celsius; maximum temperatures 34-36 degrees Celsius. Southwesterly winds 10-20 km/h.
