Bangkok: The Meteorological Department of Thailand has issued Announcement No. 11 warning of heavy to very heavy rainfall expected across various regions of Thailand from September 12 to 13, 2026. This announcement is in effect until September 13, 2026, and highlights the potential for increased rainfall, particularly in the southern region of the country. The alert extends to parts of the lower northern, northeastern, central regions, including Bangkok and its surrounding areas, and the eastern region.
According to Thai News Agency, the increased rainfall is attributed to a high-pressure system or cold air mass originating from China that is spreading over the upper northern and upper northeastern regions. This meteorological activity is coupled with a monsoon trough moving through the lower central, upper southern, upper Gulf of Thailand, and eastern regions towards a strong low-pressure system off the central coast of Vietnam. The southwest monsoon over the Andaman Sea, southern Thailand, and the Gulf of Thailand is also expected to intensify, contributing to the severe weather conditions.
Provinces expected to experience very heavy rainfall on September 12 include Ranong, Phang Nga, Prachuap Khiri Khan, and Chumphon in Southern Thailand. On September 13, Chanthaburi and Trat in the Eastern Region, along with Ranong and Phang Nga in Southern Thailand, are expected to be severely affected. Heavy rainfall is also anticipated in various other provinces, including Ubon Ratchathani in the Northeastern Region, numerous provinces in the Central Region such as Nakhon Sawan and Kanchanaburi, and several provinces in the Eastern and Southern regions.
The public is urged to remain vigilant of potential dangers such as flash floods and landslides, especially in areas on slopes near waterways and low-lying regions. The forecast predicts that a strong low-pressure system off the central coast of Vietnam may intensify into a tropical cyclone, potentially impacting the northern coast of Vietnam by September 13-14, 2026. Residents are advised to continuously monitor weather updates during this period.
For the safety of the public and to minimize potential impacts, the Meteorological Department advises careful planning of daily activities and travel. People are encouraged to follow the latest announcements and updates available on the department's website. Boat operators should exercise caution, especially small vessels, which are advised against sailing in the upper Andaman Sea from September 14-16, 2026, due to expected wave conditions exceeding 3 meters in areas with thunderstorms.