The Meteorological Department issued its second announcement warning of heavy rain in many areas from 8 to 13 September, beginning in the "Isan" region before other areas experience effects later. It warns vulnerable areas to beware of flash floods and sudden flooding.
At 17:00 on 7 September 2026, the Meteorological Department issued announcement No. 2 regarding heavy to very heavy rain over Thailand, effective from 8 to 13 September 2026. It stated that during this period, rainfall will increase with heavy rain in many areas and very heavy rain in some, starting first in the Northeast region, with other regions affected subsequently.
This is because from 8 to 11 September 2026, a monsoon trough will pass over the North, Upper Central, and Northeast regions, combined with a moderate southwest monsoon blowing over the Andaman Sea, Thailand, and the Gulf of Thailand. This will cause heavy rain in many parts of upper Thailand and very heavy rain in some areas.
Then, from 12 to 13 September 2026, a high-pressure area or cold air mass from China will extend over Upper Northern and Upper Northeastern regions, causing the monsoon trough to shift southward across Lower Central and Eastern regions. This will reach a strong low-pressure area in the central South China Sea, along with a strengthening southwest monsoon covering the Andaman Sea, the South, and the Gulf of Thailand. This will reduce rain in the North and Northeast but increase rain, including heavy to very heavy rain in some areas, in the Central region, Bangkok and its vicinity, the East, and the South.
The public, especially in Lower Northeast, Central including Bangkok and its vicinity, Eastern and Upper Southern regions during 9-11 September, should beware of dangers from heavy to very heavy rainfall and accumulated rain that may cause flash floods and runoff floods. Areas near hillsides along waterways and low-lying areas should avoid traveling on routes prone to repeated flooding, particularly low-lying zones where short-term waterlogging may occur.
Additionally, from 11 to 13 September 2026, a low-pressure area near the Philippines is likely to strengthen into a tropical cyclone and move into the central South China Sea. For safety and to minimize potential impacts, people are advised to plan their activities and travel carefully during this period.