Monsoon Rains Forming — Forecast Warns Eastern Thailand to See Heavy Downpours, Ferry Routes to Koh Samui Affected

The Meteorological Department warned on 18 July 2026 that a strengthening southwest monsoon is causing continuous rainfall across Thailand, with the eastern region expected to see heavy rain within the next 24 hours. The Gulf of Thailand and the Andaman Sea are also experiencing strong winds and waves. These conditions are directly affecting marine travel, including ferry routes linking Koh Samui with the provinces of Surat Thani and Chumphon.

Ferry operators and ports on the Krabi, Surat Thani and Chumphon sides reported that schedules have been adjusted for safety since last night. Some sailings have been canceled or postponed due to rough seas. Passengers with travel plans during this period are advised to closely monitor announcements from shipping companies and ports. Passengers should also have booking confirmations and emergency contact information ready to avoid confusion when schedules change.

Residents of Koh Samui, who rely heavily on sea transport for importing consumer goods and for tourist arrivals and departures, have been affected by the disruption of ferry services. Restaurant owners, fresh markets and tour operators say canceled sailings have delayed deliveries of supplies, driving up prices for some items such as fresh vegetables, meat and fuel. Stranded tourists may need to extend their stays, requiring accommodation managers and community resources to prepare accordingly.

Local authorities and Koh Samui’s administration have opened a central information center to advise residents and visitors on safe travel, food and water preparedness, and how to contact ferry companies and airlines if travel plans need to change. The mayor said the municipality has set aside schools and public buildings as temporary shelters if large numbers of passengers or tourists cannot leave the island, and is coordinating with public health agencies to monitor for illnesses that can arise when people are gathered in close quarters.

For travelers planning to visit Koh Samui now, tourism authorities recommend checking the latest weather updates, confirming ferry and flight schedules directly with operators, and considering travel insurance that covers force majeure for air and sea travel. If an extended stay on the island becomes necessary, visitors should plan for additional expenses and inform their accommodation, family or employer. Travelers should also follow local safety advice, such as avoiding swimming when warnings of strong winds and waves are in effect.

Although the current weather is causing concern among operators and tourists, meteorologists say such abrupt short-term changes usually subside when the monsoon shifts or a high-pressure system moves in. Preparedness and clear communication among local authorities, ferry companies and the public will help significantly reduce impacts on the local economy and inconvenience to travelers.