TMD flags flash flood risk as strong monsoon sweeps across Thailand

The Thai Meteorological Department (TMD) issued a 24-hour forecast at 5pm on Friday (June 5, 2026), saying isolated heavy rain was expected in the Northeast, the East, and the South, as well as Bangkok and its vicinity.

Isolated very heavy rain was expected in the western parts of the North and Central regions, as the rather strong southwest monsoon was prevailing over the Andaman Sea, Thailand, and the Gulf of Thailand, while a low-pressure cell was over upper Myanmar.

People in those areas were advised to be prepared and stay alert to dangers from heavy to very heavy rain and accumulated rainfall, which could cause flash floods and forest run-off, especially in risk areas near waterways and in low-lying areas.

Strong winds and waves warning: mariners should avoid thundershower areas; small boats should stay ashore

Wind waves in the upper Andaman Sea and upper Gulf of Thailand were rather strong, with waves 2-3 metres high and more than 3 metres in thundershower areas.

Mariners in the Andaman Sea and Gulf of Thailand were advised to proceed with caution and avoid sailing in thundershower areas.

Small boats in the upper Andaman Sea and the upper Gulf of Thailand should stay ashore during this period.

TMD weather forecast for Thailand from 6pm on Friday (June 5) to 6pm on Saturday (June 6)

North

• Thundershowers were expected in 70% of the area, with isolated heavy rain in Chiang Mai, Lamphun, Lampang, Phrae, Sukhothai, Kamphaeng Phet, Phitsanulok, and Phetchabun.
• Isolated very heavy rain was expected in Mae Hong Son and Tak.
• Minimum temperature 23-25°C, maximum 35-37°C.
• Southwesterly winds 10-20km/h.

Northeast

• Thundershowers were expected in 60% of the area, with isolated heavy rain in Loei, Nong Khai, Bueng Kan, Nong Bua Lamphu, Udon Thani, Sakon Nakhon, Nakhon Phanom, and Chaiyaphum.
• Minimum temperature 23-26°C, maximum 34-36°C.
• Southwesterly winds 10-20km/h.

Central region

• Thundershowers were expected in 60% of the area, with isolated heavy rain in Nakhon Sawan, Uthai Thani, Saraburi, and Ratchaburi.
• Isolated very heavy rain was expected in Kanchanaburi.
• Minimum temperature 25-27°C, maximum 34-36°C.
• Southwesterly winds 10-20km/h.

Bangkok and vicinity

• Thundershowers were expected in 60% of the area, with isolated heavy rain.
• Minimum temperature 26-28°C, maximum 33-35°C.
• Southwesterly winds 10-20km/h.

East

• Thundershowers were expected in 60% of the area, with isolated heavy rain in Nakhon Nayok, Prachinburi, Chonburi, Rayong, Chanthaburi, and Trat.
• Minimum temperature 24-28°C, maximum 32-36°C.
• Southwesterly winds 20-35km/h.
• Wave height about 2 metres, and more than 2 metres in thundershower areas.

South (east coast)

• Thundershowers were expected in 60% of the area, with isolated heavy rain in Phetchaburi, Prachuap Khiri Khan, and Chumphon.
• Minimum temperature 24-25°C, maximum 32-36°C. Southwesterly winds 20-35km/h.
• Wave height 1-2 metres, about 2 metres offshore, and more than 2 metres in thundershower areas.

South (west coast)

• Thundershowers were expected in 70% of the area, with isolated heavy rain in Ranong, Phang Nga, Phuket, and Krabi. Minimum temperature 24-25°C, maximum 30-34°C.
• From Phang Nga northwards: southwesterly winds 20-40km/h. Wave height 2-3 metres, and more than 3 metres in thundershower areas.
• From Phuket southwards: southwesterly winds 20-35km/h.Wave height about 2 metres, and more than 2 metres in thundershower areas.