Thai Meteorological Department has announced that Thailand will officially enter the rainy season on Friday, May 15, although rainfall levels this year are expected to be lower than average.
According to the department, the official start of the season is based on three key conditions: widespread rainfall across more than 60% of upper Thailand, a shift in lower-level winds to the southwest, and easterly winds at higher altitudes.
The rainy season in upper Thailand is forecast to continue until mid-October, while parts of southern Thailand’s east coast could see rainfall extending into December. Overall rainfall is expected to be around 10% below the seasonal average.
Rainfall is expected to increase gradually through mid-June, particularly in the East and western South, before easing during late June and July. Heavier rain is expected to return in August and September, raising concerns over flash floods, runoff, and overflowing rivers.
Officials are also closely monitoring the possibility of a stronger El Niño pattern developing later this year, which could bring drier conditions across Southeast Asia. One or two tropical storms are expected to affect Thailand during August and September, mainly in the North and Northeast.
The department has also opened a monitoring centre to track heavy rain and strong winds in the Andaman Sea.