Koh Samui weather

Our guide to the weather in Koh Samui during May

30

Average high

6

UV Index

155mm

Monthly rainfall

31

Sea temperature

We've looked at the most up-to-date weather data for Koh Samui, covering the last 12 years up to 2024, plus we've asked our team of travel bloggers for their first-hand experiences in order to answer the most frequently asked questions about Koh Samui weather in May.

How warm is it in Koh Samui during May?

May is typically the hottest month in Koh Samui. The temperature hits about 30℃ during the day, falling away to a balmy 28℃ at night. Of course, the high humidity will make it feel even hotter. The UV index will be high at this time of year, so protection against skin and eye damage is needed. Try to limit exposure between 10am and 4pm. Apply broad spectrum SPF 30+ sunscreen every few hours, even if it's cloudy, or more frequently after sweating or swimming, and wear UV-blocking sunglasses too, and bear in mind that bright surfaces, such as sand and water increase UV exposure.

Does it rain in Koh Samui during May?

On average, there will be 7 rainy days during the month, amounting to 154.7mm in total. That's a significant amount of rain. For comparison, the wettest months in the UK typically sees between 80mm and 100mm, depending on where you are. Due to the high temperature and humidity, you might expect lots of thunderstorms, however they're actually fairly infrequent at this time of year. On average, May will see just 6 days that produce a storm.

Is it windy in Koh Samui during May?

You're unlikely to experience any strong winds. Expect a gentle breeze that increases to moderate at times during May. The high humidity and warm temperature will make the breeze feel warm, so any cooling effect will be limted.

How warm is the sea in Koh Samui during May?

The water around Koh Samui reaches a very pleasant 31℃ during May. This is very warm, and will feel bath-like. People who normally feel the cold will find this temperature perfectly acceptable. The hot air temperature and relatively high humidity will mean that you will feel comfortably warm when coming out of the water.

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Weather in Koh Samui

Our month-by-month guide to the weather and climate in Koh Samui

27.4

Koh Samui weather in

January
27.6

Koh Samui weather in

February
28.4

Koh Samui weather in

March
29.3

Koh Samui weather in

April
30.0

Koh Samui weather in

May
29.8

Koh Samui weather in

June
29.4

Koh Samui weather in

July
29.3

Koh Samui weather in

August
29.0

Koh Samui weather in

September
28.6

Koh Samui weather in

October
28.4

Koh Samui weather in

November
27.8

Koh Samui weather in

December