Monsoon conditions heighten flash-flood risk in upper Thailand
Several northern and northeastern provinces require close monitoring from Friday to Sunday, while heavy rain is forecast in parts of four regions on Monday.
- The Thai Meteorological Department (TMD) has issued a warning for heavy to very heavy rain across upper Thailand from September 4 to 7.
- The North and Northeast regions are expected to be most affected, with specific provinces under close monitoring for very heavy rain from September 4 to 6.
- This weather event is caused by a monsoon trough moving southwards across the North and Northeast, combined with a moderate southwest monsoon.
- The public in at-risk areas, particularly hillsides and low-lying areas, is advised to take precautions against potential flash floods, forest run-off, and mudslides.
The Thai Meteorological Department (TMD) met on Thursday (September 3, 2026) to assess heavy to very heavy rain forecast across parts of Thailand from September 4 to 7.
Director-General Dr Sugunyanee Yavinchan chaired the hybrid meeting, joined by deputy directors-general Nattawut Dandee and Sravodth Somtrup, along with officials from headquarters, regional centres and weather stations.
Weather factors and affected areas from Friday (September 4) to Monday (September 7)
The meeting assessed that rainfall would increase across upper Thailand, with heavy to very heavy rain in some areas, particularly in the North and Northeast. It identified two main meteorological factors:
The monsoon trough will move southwards across the North and upper Northeast.
A moderate southwest monsoon will prevail over the Andaman Sea, Thailand and the Gulf of Thailand.
Areas requiring close monitoring by date
Friday (September 4) to Sunday (September 6)
The following provinces will require particularly close monitoring because very heavy rain is expected during this period:
- North: Chiang Rai, Phayao, Nan, Uttaradit, Phitsanulok and Phetchabun.
- Northeast: Loei, Nong Bua Lamphu, Khon Kaen, Bueng Kan, Sakon Nakhon, Nakhon Phanom, Mukdahan, Amnat Charoen and Ubon Ratchathani.
- East: Trat.
Monday (September 7)
Rainfall is expected to become more dispersed on Monday, although heavy rain is still forecast in some areas of the North, Northeast, Central and East.
Public guidance and weather warnings
The TMD issued a warning advising people in at-risk areas and places experiencing prolonged rainfall accumulation to take extra precautions against the following hazards:
- Weather hazards: flash floods, forest run-off, localised flooding and mudslides.
- High-risk locations: hillside areas near waterways, low-lying areas and places prone to recurring floods.
- Preparations: check drainage systems around homes, monitor water levels in nearby waterways and follow TMD weather forecasts and warnings closely around the clock.
