The 2026 rainy season is expected to frequently experience the phenomenon known as Rain Bomb, with Bangkok closely monitoring floodwaters pending drainage. Dry spells are predicted to trigger heavy downpours.
Mr. Somkuan Tonjan, Director of the Weather Forecasting Division and Deputy Spokesperson of the Meteorological Department, stated that based on statistics and wind patterns, the rainy season this year is expected to clearly begin officially around mid-May or during the third week of May, with full rainy season conditions from 12-14 May.
Although the 2026 rainy season will begin as expected, intermittent dry spells and variable weather conditions are anticipated before its onset. This includes alternating hot, sunny days and occasional rain. Once the rainy season starts, dry spells may occur from June to mid-July due to the monsoon trough shifting northward, reducing moisture. These dry spells may be more pronounced than last year.
Additionally, the El Niño phenomenon and related changes are influencing the weather. Currently, the climate is transitioning from La Niña to El Niño, with these cycles now shortening from the usual 5-7 years to about 2-3 years. This year, El Niño is expected to impact rainfall, potentially causing amounts to be below or near average, though not reaching a "super El Niño" level.
The likelihood of "Rain Bombs"—sudden, intense localized heavy rain—remains high this year due to fluctuating weather conditions between extreme heat, dryness, and humidity, which create atmospheric instability. Especially during dry spells, when moisture encounters hot air, severe thunderstorms are more likely. The chance of Rain Bombs extends through August and September, but once the air is fully saturated with moisture, rainfall will return to normal seasonal patterns.
In the 2026 rainy season, Bangkok remains at risk for heavy rainfall. Currently, rain mostly falls in northern areas such as Don Mueang, Rangsit, Pathum Thani, and Nonthaburi.
After 14 May, as the southwest monsoon strengthens, it will bring more rain into inner Bangkok in the afternoons and evenings, increasing the risk of short-term flooding awaiting drainage. However, prolonged flooding lasting several days is not expected.
Citizens are advised not to panic over the concept of a super El Niño and to follow information updates from the Meteorological Department calmly.
If rainfall this year is below or near normal, water usage should be planned carefully for activities requiring large amounts, to prepare for conditions extending into next year.
Residents of Bangkok should prepare for traffic disruptions and temporary flooding during heavy rain periods.
