Heavy rain risk grows as southwest monsoon strengthens in Thailand
Rain is forecast to increase across upper Thailand from Thursday (June 25, 2026) to Saturday (June 27, 2026), with heavy falls in some areas.
- A strengthening southwest monsoon is forecast to increase rainfall across Thailand, with a heightened risk of heavy rain from Thursday, June 25, to Saturday, June 27.
- The Thai Meteorological Department has warned of potential flash floods, forest run-off, and river overflows, particularly in foothill and low-lying areas.
- The strengthening monsoon will also cause higher waves in the Andaman Sea and Gulf of Thailand, prompting a caution for boat operators to navigate carefully and avoid thunderstorm areas.
The Thai Meteorological Department (TMD) released its weather forecast, saying that between Monday (June 22, 2026) and Wednesday (June 24, 2026), upper Thailand will see thunderstorms in some areas, while the South will still have heavy rain in some places as the southwest monsoon continues to prevail over the Andaman Sea, Thailand and the Gulf of Thailand.
During the same period, waves in the upper Andaman Sea will be about 1-2 metres high, while waves in the lower Andaman Sea and the Gulf of Thailand will be about 1 metre.
In thunderstorm areas, waves may exceed 2 metres.
After that, from Thursday (June 25) to Saturday (June 27), rainfall is expected to increase across upper Thailand, with heavy rain in some areas, as the southwest monsoon strengthens and a low-pressure cell covers upper Vietnam.
The conditions will leave many areas at risk of heavy rain and accumulated rainfall.
Wind and waves in the upper Andaman Sea will also strengthen, with waves about 2 metres high.
Waves in the lower Andaman Sea and upper Gulf of Thailand will be 1-2 metres high, and in thunderstorm areas, they may exceed 2 metres.
The Thai Meteorological Department urged people nationwide, especially those in foothill areas, near waterways and in low-lying areas, to watch for dangers from heavy rain and accumulated rainfall, which could cause flash floods, run-off from forests and river overflows.
Boat operators in the Andaman Sea and the Gulf of Thailand are also advised to navigate with caution and avoid sailing in thunderstorm areas throughout the period.
