Thailand —
The Thai Meteorological Department has declared the official start of the rainy season, effective May 15th, 2026, with forecasts indicating that overall rainfall will be lower than last year and below the long-term average. The announcement was made by Dr. Sukanyanee Yawinyan, Director-General of the Meteorological Department, during a press briefing at the Weather Forecast Operations Center in Bangkok.
Meteorological indicators confirmed the onset of the rainy season: Widespread rainfall covering more than 60% of northern Thailand, a shift in lower-level winds to southwesterly, and upper-level winds turning easterly. Rainfall in northern and central regions is expected to continue until mid-October, while the eastern coast of southern Thailand will see rain through December.
This year’s rainfall is projected to be about 10% below average. Rainfall will gradually increase from mid-May to mid-June, particularly in the east and the west coast of southern Thailand, where heavy downpours are likely. However, late June to early July may bring a dry spell, especially in non-irrigated areas, before rains intensify again in August and September. These months will pose the highest risk of flash floods, landslides, and river overflows.
The department is closely monitoring the El Niño–Southern Oscillation (ENSO). Current conditions remain neutral, but a transition to El Niño is likely in the second half of the year. This could further reduce rainfall and slightly raise temperatures nationwide.
Despite the overall decline in rainfall, heavy storms driven by monsoon systems and low-pressure cells remain a concern. Tropical cyclones may also affect Thailand, with one to two storms expected to impact the country between August and September, particularly in the north and northeast.
Between May 14–18, strong low-pressure activity over the Bay of Bengal combined with an intensifying southwest monsoon is expected to bring heavy to very heavy rainfall across northern, central, eastern, and southern regions. The Andaman Sea will see waves of 2–3 meters, rising above 3 meters during thunderstorms. Small boats in the Andaman are advised to remain ashore, while larger vessels should navigate with caution.
To strengthen monitoring and response, the Meteorological Department has launched a new Heavy Rain and Rough Seas Monitoring Center. The center will track weather developments and issue timely warnings throughout the rainy season. Authorities urge the public to stay alert to official forecasts and advisories, especially in flood-prone and coastal areas.
For the original version of this article, please visit The Pattaya News.
