Gulf of Thailand weather forecast at a glance
The Gulf of Thailand weather forecast for Samui, Phangan, Tao and Surat Thani covers 29 September to 4 October, 2025, and points to a wet, gradually improving week across the islands and the mainland pier area. Rain coverage eases from 60% to 40% of the area, winds drop from 19 km/h to 13 km/h, and wave heights settle from 1–2 m down to around 1 m. Use it to plan sailings, transfers and connections before you book.
Day-by-day outlook, 29 September to 4 October, 2025
- 29 Sep (Monday) Temp: 32°C / 25°C. Weather: Heavy rain, thunderstorms (60% area). Wind: 19 km/h. Sailing: Caution advised, waves 1–2 m. Tide: Moderate tides.
- 30 Sep (Tuesday) Temp: 32°C / 25°C. Weather: Heavy rain (60% area). Wind: 19 km/h. Sailing: Risky for small boats, waves up to 2 m. Tide: Normal patterns.
- 01 Oct (Wednesday) Temp: 34°C / 25°C. Weather: Heavy rain (40% area). Wind: 17 km/h. Sailing: Slightly calmer, waves 1–1.5 m. Tide: Regular tides.
- 02 Oct (Thursday) Temp: 34°C / 25°C. Weather: Heavy rain (40% area). Wind: 15 km/h. Sailing: Conditions improving, waves around 1 m. Tide: Normal.
- 03 Oct (Friday) Temp: 35°C / 26°C. Weather: Heavy rain (40% area). Wind: 13 km/h. Sailing: Relatively better, waves 1 m or less. Tide: Standard tides.
- 04 Oct (Saturday) Temp: 35°C / 26°C. Weather: Heavy rain (40% area). Wind: 13 km/h. Sailing: Manageable but monitor local alerts, waves 1 m. Tide: Normal fluctuations.
What changed across the week
The rougher half sits at the front. Monday and Tuesday carry the highest rain coverage, the strongest winds and the biggest seas, with Monday also bringing thunderstorms. From Wednesday onward the trend is one way: less rain coverage, lighter wind each day, and waves easing to 1 m or less by Friday. Daytime highs climb from 32°C to 35°C, while overnight lows barely move, from 25°C to 26°C.
Who this affects
Wave height matters most to smaller craft, so speedboat and small-vessel services are the first to feel a 2 m sea, while larger car ferries generally handle it better. Tuesday is explicitly flagged as risky for small boats. Land services are affected differently: heavy rain can slow buses, minivans and private transfers on the approach roads to piers, so leave extra buffer between a road leg and a boat departure.
Practical impact on your trip
Build in flexibility on 29 and 30 September. Keep contact details current so the operator can reach you if a departure is retimed, and avoid booking a tight onward flight or connection on the roughest days. Tides stay moderate to normal throughout, so no unusual tidal restrictions are indicated for this period.
Routes to check
Conditions here apply to island-hopping and mainland crossings alike. Compare departures on the Surat Thani to Koh Samui route, the Koh Samui to Koh Phangan crossing and onward services to Koh Tao, then pick a departure that suits the calmer part of the week.
Disclaimer: Weather, sea conditions, and tide information are subject to change. Always check local updates and forecasts before planning activities.
Live timetables, operators, journey times and fares are shown at the point of booking. Search availability for your dates to see what is running.
