September Forecast: Heavy Rain Expected Nationwide
Thailand's meteorological department warns of heavy rainfall and thunderstorms affecting 60-80 percent of the country in September, with risks of flash floods and a tropical cyclone potentially approaching Thai territory.
The Thai Meteorological Department has issued its September 2025 weather outlook, predicting another month of persistent and heavy rainfall nationwide. Thunderstorms are expected to affect 60-80 percent of the country throughout the month, with some areas experiencing extremely intense downpours that could trigger flash floods, flooding, and overbank flooding. Overall rainfall is expected to be about 10 percent below normal, except in the North where it will be 20 percent below normal and the East where it will be 10 percent above normal. Strong southwest monsoon winds will continue across the Andaman Sea and upper Gulf of Thailand, with waves reaching 2-3 meters in parts of the Andaman and upper Gulf, and 1-2 meters in the lower Gulf. Additionally, a tropical cyclone is expected to develop in the South China Sea with a high probability of approaching or crossing Thai territory. The public is advised to monitor weather forecasts and warnings from the meteorological department continuously.
