Thailand braces for heavy rain in Sept-Oct 2025, drought risk looms in 2026

In an era of increasingly volatile weather, climate instability is no longer just a phrase—it is evident in intensifying and unpredictable floods and droughts every year. Thailand now faces a new challenge as forecasts from both domestic and international sources indicate above-average rainfall from September to October 2025, raising the risk of flooding in many areas. Meanwhile, El Niño is likely to return in 2026, potentially delaying the monsoon season and bringing severe droughts and heatwaves.

Assoc Prof Witsanu Attavanich, a lecturer in the Department of Economics at Kasetsart University and spokesperson for the ad hoc committee reviewing the Clean Air Act draft, provided an update on Thailand’s flood and drought situation. He said that September-October 2025 will see La Niña influence, resulting in heavier-than-average rainfall across almost all regions, particularly Northeast, North, and Eastern Thailand, increasing the risk of severe flooding. In contrast, southern Thailand is expected to experience below-average rainfall in September, but from October onwards, especially in the Upper South, rainfall is projected to rise, requiring close flood monitoring.

From November 2025 to February 2026, rainfall is expected to be close to average in most regions, except in the South, where below-average precipitation may reduce water reserves ahead of the next dry season.

According to the US Climate Prediction Center (NOAA), the world is currently in a Neutral Phase and will enter a weak to moderate La Niña briefly between October and December 2025, before returning to normal in January 2026. Meanwhile, the likelihood of El Niño is gradually increasing.

The European ECMWF predicts the Neutral Phase will end around April 2026, with El Niño developing from May 2026 onwards, ranging from mild to severe. This could delay the 2026 monsoon and increase the risk of heatwaves and drought.

Forecast averages from over 12 global meteorological agencies, including Columbia University’s IRI, converge on the same prediction: rainfall will exceed average levels in September-October 2025, with Northeast, Eastern, and Upper Southern Thailand being most at risk of flooding.

Witsanu concluded that the public should prepare for heavier-than-normal rainfall this year, particularly in September-October, while managing water resources carefully to store reserves for the potentially severe drought in 2026. He also urged everyone to closely monitor weather forecasts in this era of global climate instability.