Koh Samui and Koh Chang sit on opposite ends of the Gulf of Thailand coastline but share the same fundamental seasonal pattern — a long dry season that makes for excellent island riding, and a rainy season that brings the islands to life in a different but equally rewarding way.
The Two Seasons of the Gulf Coast Islands
Dry Season — January to September
The Gulf coast enjoys a long dry season covering the majority of the year. From January through to September, conditions on both islands are generally clear, warm and excellent for riding. Temperatures of 28 to 35°C, with sea breezes moderating the heat along coastal roads.
Rainy Season — October to December
The Gulf coast rainy season peaks from October through December — the opposite of the Andaman coast. Rain can be heavy and sustained during October and November. The combination of wet roads and steep interior terrain on both islands requires extra care. The islands during the rainy season are green, dramatic and beautiful — accommodation prices drop, crowds thin, and the islands take on a quieter, more authentic character.
Month by Month
| Month | Conditions for Riding |
|---|---|
| January | Excellent dry season riding. Cool, clear and comfortable. One of the finest months on both islands. |
| February | Outstanding conditions continuing. Peak dry season at its best. |
| March | Still excellent. Temperatures climbing gently. Sea breeze keeps coastal riding comfortable. |
| April | Hot and dry. Songkran brings celebrations to the island towns. Early morning riding is most comfortable. |
| May | Warm and generally dry. A good riding month with the islands beginning to quieten from peak season. |
| June | Dry season continuing. Warm, clear and quiet. An underrated month to ride the Gulf islands. |
| July | Still largely dry on the Gulf coast. Good riding conditions with lighter tourist traffic. |
| August | Warm and generally clear. One of the quieter months on both islands. |
| September | Dry season beginning to transition. Conditions still good but occasional showers possible toward month's end. |
| October | Rainy season arriving. Rain becoming more frequent and heavy. Extra care on the island roads. |
| November | Peak rainy season. Heaviest rainfall of the year. Riding possible but flexibility and waterproofs are essential. |
| December | Rain easing through the month. Conditions improving toward month's end as dry season begins to return. |
Best Months to Ride on the Gulf Coast
January through March are the standout months. April through August is an excellent extended window — the dry season on the Gulf coast is long and generous.
Making the Most of the Rainy Season
The 7am to 11am morning window is the most reliable riding period. Plan to be settled at your destination before early afternoon. The steep interior roads on both Koh Samui and Koh Chang deserve particular respect in wet conditions. Stick to the coastal ring roads in heavy rain. A lightweight waterproof jacket, an early start and a relaxed attitude to the afternoon weather is all you need to enjoy the islands in any month of the year.
Planning to ride Koh Samui as part of The Beach Run?
Check our full route guide for Phuket, Koh Samui and Krabi.
The Beach Run Route Guide →