Monsoon in Thailand: understanding the rainy season (and traveling anyway)
Understanding the weather · 2 min read · Updated on August 16, 2026
What is the monsoon in Thailand?
The southwest monsoon brings moisture-laden winds from the Indian Ocean from May to October. It mainly drenches the Andaman coast (Phuket, Krabi, the southern islands) with heavy downpours in the late afternoon, while the Gulf of Thailand stays noticeably more sheltered.
Contrary to popular belief, the monsoon does not mean it rains all day: showers are often short and intense, followed by bright spells.
Two coasts, two rainfall patterns
This is the key point: Thailand has two coastlines with almost opposite climates. When the Andaman coast is under rain (May to October), the Gulf of Thailand enjoys its dry summer, especially in July and August.
Conversely, the gulf (Koh Samui, Koh Phangan, Koh Tao) peaks in rainfall from October to December, a period when the Andaman returns to sunshine.
- Andaman coast: dry season from November to April, rains from May to October.
- Gulf of Thailand: fine summer from June to August, marked rains from October to December.
Traveling during the rainy season: a good idea?
Yes, if you choose the right coast. Traveling in Thailand in August can be excellent... provided you aim for Koh Samui or Koh Tao rather than Phuket. Prices are lower, sites less crowded, and the sun remains generous on the sheltered coast.
The real trap is relying on a national average: it's the region-by-region comparison that matters.
The month to avoid (and the one to favor)
October and November are the trickiest months across the country, because that is when both coasts can be rained on at the same time. January, February and August, on the other hand, are excellent choices depending on the region you're targeting.
Frequently asked questions
Does it rain all day during the monsoon in Thailand?
No. Monsoon rains are generally short, intense showers, often late in the day, interspersed with sunny spells.
What is the best time to avoid the monsoon?
From November to February on the Andaman coast, and from June to August in the Gulf of Thailand. The choice depends on the region you want to visit.
Is Koh Samui spared by the monsoon?
Koh Samui follows the gulf pattern: its summer (July-August) is fairly dry, but the island receives a lot of rain in October and November.