When is the best time to go to Koh Samui?

The best time to visit Koh Samui is from February to May, and then in July and August. However, it is possible to consider a trip almost all year round, with only the month of November really to be avoided due to the rain.

Between February and April is when the atmosphere is driest. It is hot, without being stifling, and you will enjoy a clear blue sky every day. In December-January and July-August, the humidity level is higher, but not uncomfortable.

On the flip side, these are the months with the highest tourist influx. Indeed, the island is a paradise for Europeans craving sunshine in winter and taking advantage of long summer holidays to explore Thailand. As a result, prices are at their highest, whether for flights or accommodation on site. It is essential to make your reservations as early as possible to hope for reasonable prices and availability.

When to visit Koh Samui without breaking the bank? The best compromise is to travel in May, June, September, or October. While the weather may not always be perfect, it mostly consists of refreshing showers in the late afternoon, quickly followed by the return of the sun.

Lastly, if you want to go diving in Koh Samui, know that visibility is at its maximum (around 30 m) between July and September. But if you dream of swimming among whale sharks, the ideal time is from March to May, as well as September-October when plankton concentration is highest in the area and they come to feed. Note that these ocean giants are often near the surface, making it easy to observe them, even while snorkeling.

Annual weather on the island of Koh Samui

For information about the climate and the weather city by city on the island of Koh Samui for a specific month, click on the corresponding line below:

January 81°F to 83°F
10 to 11 days*
February 83°F
5 days
March 85°F
6 to 7 days*
April 86°F
8 to 9 days*
May 88°F
11 to 14 days*
June 86°F
12 to 15 days*
July 86°F
11 to 14 days*
August 86°F
9 to 14 days*
September 85°F
12 to 16 days*
October 85°F
18 to 19 days*
November 85°F
21 days
December 85°F
14 to 15 days*
* weather varies across the country

Best time to travel to Koh Samui by cities

Chargement en cours

Climate and Weather on the island of Koh Samui

Koh Samui is located in the Gulf of Thailand, 700 kilometers south of Bangkok by air, at the heart of an archipelago of 85 islets, including 6 inhabited ones, which make up the Mu Ko Ang Thong Marine National Park. Its famous neighbors include Koh Tao (THE diving destination in Asia) and Koh Phangan (known for its wild Full Moon Parties). It is renowned for having nearly three million coconut trees! It is the third largest island in Thailand.

As in most Thai regions, the climate in Koh Samui is tropical monsoon.

However, the climatic seasons are shifted compared to areas on the west coast and in the Andaman Sea, such as Krabi, Phuket, or Koh Phi Phi, where July and August can experience intense rainy seasons.

Therefore, due to its geographical position, the island is relatively well protected from storms, and the weather in Koh Samui is hot all year round, with variations in humidity levels and precipitation depending on the months.

Koh Samui: Silver Beach à Koh Samui

The Cool Season in Koh Samui (FEBRUARY - MARCH)

In addition to being the driest period of the year, February and March are the coolest months. The temperatures range between 28 and 29°C (85°F) during the day and about 1°C (34°F) lower at night. The water temperature remains around 29°C (85°F) . If you tend to suffer from the heat, this period is ideal for staying in Koh Samui!

In terms of precipitation, rains are rare in February-March, but not non-existent: there is a 16 to 20% chance of showers, mostly occurring at night and not a major inconvenience.

The Hot Season in Koh Samui (APRIL - AUGUST)

As the name suggests, temperatures gradually rise during this season. While April averages around 30°C (86°F) , May reaches highs of around 31°C (88°F) both in the air and water, making it the hottest month of the year. Peaks of 35°C (95°F) are quite common.

From June to August, the temperature drops to 30°C (86°F) , but humidity levels increase and the sensation of heat intensifies. During this period, expect between 9 and 15 days of rain, with June being the wettest month. However, it is important to note that showers can be intense but short-lived, with the sky clearing quickly after the rain passes.

The Rainy Season in Koh Samui (SEPTEMBER - JANUARY)

This period is also known as the monsoon season. It involves warm and humid air coming from the Indian Ocean carried by the east winds.

Despite this, temperatures remain warm: around 29°C (85°F) in the air and 30°C (86°F) in the water, with a slight cooling in January where averages are closer to 28°C (83°F) .

Rain occurs on some days, in the form of refreshing tropical showers that do not last long. This is followed by very sunny days, but with high humidity levels. November and, to a lesser extent, October are the rainiest months, with up to a 71% chance of showers. The advantage of this season is that the vegetation provides stunning landscapes.

Temperatures and rainfall on the island of Koh Samui

On these 3 graphs, we present the evolution of temperatures of Koh Samui and month-by-month rainfall for the cities of Chaweng Beach, Bang Kao (Laem Sor beach), Bophut, Choeng Mon and Koh Madsum, as well as the month-by-month sea temperature for coastal cities.

Peak visitor numbers and tourist seasons on the island of Koh Samui

Find out when Koh Samui has its high tourist season (the period when the influx of tourists is highest) and off-peak tourist season using our data and figures.

Tourist seasons on the island of Koh Samui

The months with low numbers of tourists are: March, April, May, June, September, October and November. The number of visitors to Koh Samui is high in: January, February, July, August and December.

  • Very low season on the island of Koh Samui: November.
  • Low season on the island of Koh Samui: March, April, May, June, September and October.
  • High season on the island of Koh Samui: January, February, July and December.
  • Peak season on the island of Koh Samui: August.

Figure: Visitor index for Koh Samui month by month

Where to go on the island of Koh Samui?

This table allows you to see the maximum temperature for each city and our opinion on the weather month by month (see colour legend below the table).

Cities jan.feb.mar.apr.mayjun.jul.aug.sep.oct.nov.dec.
Chaweng Beach83°F83°F85°F86°F88°F86°F86°F86°F86°F85°F85°F85°F
Bang Kao (Laem Sor beach)83°F83°F85°F86°F88°F86°F86°F86°F86°F85°F85°F85°F
Choeng Mon83°F83°F85°F86°F88°F86°F86°F86°F86°F85°F85°F85°F
Koh Madsum83°F83°F85°F86°F88°F86°F86°F86°F86°F85°F85°F85°F
Koh Phaluai83°F83°F85°F86°F88°F86°F86°F86°F85°F85°F85°F85°F
Koh Taen83°F83°F85°F86°F88°F86°F86°F86°F86°F85°F85°F85°F
Lamai beach83°F83°F85°F86°F88°F86°F86°F86°F86°F85°F85°F85°F
Lipa Noi83°F83°F85°F86°F88°F86°F86°F86°F86°F85°F85°F85°F


good weather

tolerable weather

very bad weather

About Koh Samui

What can I do on the island of Koh Samui?

Beaches / swimming

Nature and countryside

Culture and heritage


Family travel

Crafts / shopping



Is this weather information for Koh Samui reliable?

Climate data for Koh Samui has been gathered every day since January 2009. The analysis of these meteorological data for Koh Samui allows us to determine the average for each month in Chaweng Beach, Bang Kao (Laem Sor beach), Bophut, Choeng Mon, Koh Madsum, Koh Phaluai, Koh Taen, Lamai beach, and 3 other cities.

So yes: this data is reliable except in cases of temporary climate disruption in the region.

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