On 11 November 2026, Koh Samui island experienced heavy rainfall exceeding 120 mm in 12 hours, causing flooding, landslides and major disruptions to traffic and electricity.
In the district of Koh Samui, continuous torrential rain led to an accumulation of more than 120 millimetres of water in twelve hours. This situation generated several types of simultaneous incidents across many areas of the island.
From the afternoon onwards, standing water accumulated on several roads awaiting drainage. Flash flooding affected homes in low-lying areas, with water levels sometimes reaching around one metre. Mountain torrents surged near waterfalls and down slopes, while landslides were reported in at-risk zones.
In some places, widespread power cuts lasted more than ten hours, linked to repair and network improvement works scheduled by the electricity authority. Mobile access points and internet connections were also disconnected, making internet connections very slow. Traffic was also severely slowed on many routes, roughly tripling usual journey times.
From 4pm, the authorities responded by issuing alerts via the “Cell Broadcast” system, declaring the affected areas and setting up emergency assistance for victims. Officers were deployed to ease traffic using diversion routes, while pumps were installed to speed up drainage in low-lying areas and flooded roads.
Vigilance remains essential due to the risks of further heavy rain, flooding, torrents and landslides, particularly in low-lying areas, on slopes and near waterfalls. Work to restore the electricity network continues according to the established schedule.
This episode highlights Koh Samui’s vulnerability to intense rainfall, which can simultaneously trigger flooding, mudflows and disruption to essential infrastructure. The services concerned continue to coordinate action to limit the impact on residents.
Local source