The Thai Meteorological Department (TMD) issued a weather advisory on Monday warning of heavy to very heavy rainfall across 41 provinces, including the Bangkok Metropolitan Region. The warning, effective through Wednesday, cites a monsoon trough and southwesterly monsoon as the cause for the anticipated weather conditions.
According to the department’s announcement, the active monsoon trough is situated over the northern and northeastern regions of the country. This system, combined with a moderate southwesterly monsoon prevailing over the Andaman Sea, the Gulf of Thailand, and southern Thailand, is expected to increase rainfall, leading to isolated heavy and very heavy downpours.
The TMD specified that six provinces in the eastern and southern regions are forecast to experience “very heavy rain”: Trat, Ranong, Phang Nga, Phuket, Krabi, and Trang. An additional 35 provinces across the northern, northeastern, central, and eastern regions were placed under a “heavy rain” alert. For the Bangkok Metropolitan Region, the forecast indicated thundershowers were expected over 70% of the area.
In its statement, the department cautioned the public in the affected areas to be aware of the potential for flash floods and forest runoff, particularly in hillside areas near waterways and in low-lying areas.
The weather advisory also included specific warnings for maritime activities. The TMD forecast that waves in the upper Andaman Sea and the upper Gulf of Thailand could reach heights of two to three meters. During thunderstorms, wave heights could exceed three meters. Operators of all vessels in these areas were advised to navigate with caution and avoid storm-affected zones. The department specifically recommended that small boats in the upper Andaman Sea and upper Gulf of Thailand remain ashore until conditions improve.
This weather pattern is consistent with Thailand’s annual rainy season, which typically lasts from May to October and is characterized by the influence of monsoon weather systems. Government agencies use the TMD’s forecasts to prepare for potential impacts and to inform residents in at-risk locations.
