Bangkok: May 15th officially marks the start of the rainy season in Thailand. The Meteorological Department has issued a warning that the rainfall in 2026 is expected to be 10% less than normal and has inaugurated a center to monitor heavy rain and strong winds.
According to Thai News Agency, Dr. Sukanyanee Yawinchan, Director-General of the Meteorological Department, announced today the beginning of the rainy season for 2026 and the opening of the "Heavy Rainfall Monitoring Center for Thailand and Strong Winds and Waves in the Andaman Sea" at the Weather Forecasting Operations Center. The department confirmed that meteorological conditions meet the criteria for the onset of the rainy season, such as rainfall covering more than 60% of upper Thailand and shifts in wind patterns.
The rainy season in upper Thailand is expected to last until mid-October, while the eastern coast of southern Thailand will receive rain until December. Nationwide rainfall is projected to be lower than in 2025 and about 10% below the normal average. Rainfall will become more consistent from mid-May to mid-June, especially in southern Thailand's eastern and western regions, where heavy rain might occur in some areas.
From late June to early July, rainfall is likely to decrease, potentially causing droughts in areas outside irrigated zones before heavy rains return in August and September. This period demands attention to potential flash floods, landslides, and river overflows.
The Meteorological Department is also monitoring the El Ni±o-La Ni±a (ENSO) phenomenon, which is currently neutral but may shift to an El Ni±o state in the latter half of the year. This could lead to reduced rainfall and slightly higher temperatures.
Despite the overall lower annual rainfall forecast, vigilance is advised due to possible heavy monsoon rains and low-pressure systems, which could trigger flash floods and landslides, impacting agricultural regions.
Regarding tropical cyclones, 1-2 storms may affect Thailand, primarily in the northern and northeastern regions, likely occurring in August and September.
The monitoring center will closely analyze and assess weather conditions, particularly from May 14-18, 2026, due to expected heavy rainfall in the North, Central, East, and South, influenced by a low-pressure system in the Bay of Bengal and a strong southwest monsoon.
Strong winds and rough seas are anticipated in the Andaman Sea and the Gulf of Thailand, with waves reaching 2-3 meters, or over 3 meters during thunderstorms. Residents in vulnerable areas should prepare for flash floods and landslides, and boat owners are advised to exercise caution, with small boats refraining from leaving shore.
The Meteorological Department will continue to monitor and issue warnings, urging the public to stay informed through weather forecasts and warnings throughout the rainy season.