Flash Floods in Southern Thailand: Why the Water Arrives Early | RainViewer Blog

TL;DR: A flash flood happens when rain arrives faster than the ground, the canals and the drainage can take it, which does not depend on the total alone. A flash flood means flooding that begins less than 6 hours after the rain. Hat Yai recorded 335 millimetres (13.2 inches) of rain on 21 November 2025 and 630 millimetres (24.8 inches) over 72 hours, according to the Department of Disaster Prevention and Mitigation.