Gulf of Thailand weather and tide forecast: what changed this week
The weather and tide forecast for the Gulf of Thailand (Samui/Phangan/Tao/Surat Thani) has been updated for 21–26 July 2025, and the headline is a strengthening southwest monsoon. Daytime highs stay warm at roughly 27–37 °C all week, but sea state — not temperature — is what matters for anyone holding a ferry ticket.
Gulf of Thailand Weather Forecast (Samui/Phangan/Tao/Surat Thani) July 21 to 26 July, 2025
Monday, July 21
Temperature: ~27–35 °C. Weather: Scattered to fairly widespread thundershowers, isolated heavy rain. Sailing Conditions: Rough — waves 2–3 m, above 3 m in thunder cells. Tide: High early morning, low afternoon.
Tuesday, July 22
Temperature: ~27–36 °C. Weather: Widespread thundershowers, isolated heavy to very heavy rain. Sailing Conditions: Rough — similar wave heights (2–3 m, >3 m in storms). Tide: Low mid-morning, high late afternoon.
Wednesday, July 23
Temperature: ~27–35 °C. Weather: Scattered to widespread thundershowers, heavy rain possible. Sailing Conditions: Rough — waves mostly 2–3 m, rising to over 3 m in cells. Tide: Low late morning, high early evening.
Thursday, July 24
Temperature: ~27–35 °C. Weather: Scattered thundershowers and isolated heavy rain. Sailing Conditions: Rough — 2–3 m waves, above 3 m in thunder areas. Tide: Low early afternoon, rising overnight.
Friday, July 25
Temperature: ~28–36 °C. Weather: Scattered to fairly widespread showers, isolated heavy rain. Sailing Conditions: Rough — consistent with 2–3 m waves, >3 m in storms. Tide: Low midday, high evening.
Saturday, July 26
Temperature: ~27–37 °C. Weather: Scattered showers, thunderstorms possible. Sailing Conditions: Rough — expect 2–3 m waves, over 3 m in thunder cells. Tide: Late morning low, late evening high.
Sea state and monsoon summary
The southwest monsoon strengthens over the Gulf—wind speeds 15–35 km/h (8–18 knots) (tmd.go.th).
Expect consistently rough seas; small boats should remain ashore, while larger vessels must steer clear of thunderstorm cells (tmd.go.th).
Who and what this affects
Rough seas in the Gulf of Thailand affect island crossings most. Smaller, faster craft are the first to be held in port, while larger vehicle and passenger ferries are more likely to keep sailing but may run late while avoiding thunderstorm cells. Mainland journeys by bus, minivan and private transfer are less exposed to wave height, though heavy rain can still slow road travel around Surat Thani.
Combined tickets that pair a road leg with a boat leg are the most sensitive: a delay on either side can affect the connection. Check the operator and vessel type shown on your booking, as conditions are felt differently by each.
Practical tips for travellers
- Travel on the earlier departures where you can — thundershowers in the Gulf often build through the afternoon.
- Leave a buffer before flights and onward connections rather than booking the last crossing of the day.
- Sit mid-ship and low down if you are prone to seasickness in 2–3 m waves.
- Keep phones, documents and electronics in a dry bag; open decks and piers get soaked in heavy rain.
- Re-check departures on the morning of travel, and note the cancellation and change conditions shown at booking.
Routes to check before you book
Live departure times, operators, journey times and prices are shown on each route page at the moment you search. Compare options for Surat Thani to Koh Samui ferries, Koh Samui to Koh Phangan crossings and Koh Phangan to Koh Tao services, or browse everything serving Koh Tao.
Disclaimer: Weather, sea conditions, and tide information are subject to change. Always check local updates and forecasts before planning activities.
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Note for the site team: the internal links above use placeholder URL patterns and the forecast dates are historic (July 2025) — please swap in live route variables and refresh the forecast window before publishing.
