At most times of the year visitors will enjoy kind weather on Samui and the surrounding coastal areas. During the high season (December to February), temperatures on Samui hover around 30°C; the seas at this time of year are calm and generally clear and breezes are light. Sporadic tropical downpours can occur in December, but this is still considered the best season to visit as the weather is cooler than later in the year.
From March to June the weather can get very hot on Samui, up to 40C° (that’s 100°F)! There is little to no rain during these months – which can cause water shortages – and the pace of life slows right down to compensate for the heat. The sea remains calm and low tides can lead to very shallow waters on the island’s beaches. The wind picks up again in May and this is a popular time for off-season visits. Late in the afternoon, huge thunderstorms sometimes build offshore and come crashing into the island.
The weather on Samui during July-September is slightly cooler, with a mini-monsoon season that brings occasional storms and periods of heavy rain. These are also popular months for visitors, who can still guarantee plenty of sunshine during their holiday.
October and November see more rain than the other months, although even then it doesn’t normally rain every day. Unlike many other parts of the country, Koh Samui doesn’t have a prolonged or predictable rainy season. During the wettest periods, for example, there are rarely more for than two or three days without sun, even during November; which is commonly considered to be the monsoon. However, the weather in Samui is quite difficult to predict during this time and the seas can be unusually rough.
No matter which season you decide to visit Koh Samui, as a tourist, one thing you will rarely feel is cold as the island enjoys warm, tropical weather.
Koh Samui monthly weather guide
Weather in Samui in January
After the New Year has hit, the island’s weather is quite temperamental. The northeast monsoon season has departed and it starts getting warmer, but still with a chance of rain. If it does decide to shower, it should only be a short burst. This is the most popular season and hotels can be full and premium priced.
Weather in Samui in February
Generally, this time of year sees a dramatic reduction in winds when windsurfing and kite-surfing (on the east of the island) water sports come to a standstill. Temperatures are hitting the mid-30s (°C) by day and there is not much let-up at night. The weather in Samui remains dry in February; thus, this is a popular time to visit.
Weather in Samui in March
Although the weather is warm in Samui in March, this is an ideal time to take trips out to the neighbouring islands if boats are not your favourite mode of transport. The seas are generally tranquil and it makes ideal weather to scuba dive and snorkel. However, the sun is reaching its daytime peak and it can become unbearable in the midday heat.
Weather in Samui in April
April is traditionally the hottest month of the year in Samui. The Sonkran water festival takes place mid-April and it makes for the best way to cool down. If you see rain, you will be blessed as it does not happen often at this time. Expect temperatures in the 40s, and without the benefit of sea breezes.
Weather in Samui in May
The season quietens down on Samui from May onwards; the weather remains hot, while rains are yet to arrive. You can get good discounts on hotel rooms at this time, while also enjoying plenty of sunshine, but be careful of sunburn!
Weather in Samui in June
From the middle of the year in June, the weather will start its long transition into the rainy season. The rainfall average will remain steady for the next four months and temperatures will decline. This doesn’t mean it gets cold – far from it – more it cools off a little and becomes sticky and humid due to cloud cover.
Weather in Samui in July
The start of the European school summer holidays brings unusual weather to Samui and the surrounding islands in July. Hotels and guesthouses start to get busier and the weather can be volatile, with crashing waves on a rainy day to sunshine and still air the next, so it really can be hit and miss.
Weather in Samui in August
As the schools have finished, the influx of backpackers heading to the island rises quite dramatically. Many head over to Koh Pha Ngan to relax, but there’s no real need to book in advance and prices are ‘low season’ rates. As in July, the daily weather can be quite random – hot and sunny one day, rainy and windy the next.
Weather in Samui in September
Heading out of the summer season in September can be the start of the infamous Samui rainy season. Temperatures do not fluctuate much throughout the year, although even slightly higher ground at night can be cooler. September is one of the quietest months on the island, yet can still be pleasant.
Weather in Samui in October
The rainy season has touched down officially, so remember your umbrella as you will likely need it. There is still time to sunbathe, but if you are there for two weeks do not plan on a deep tan.
Weather in Samui in November
This is possibly the only time of year you may want to avoid because of the weather. November can see flash floods around the island and although the local council has worked on installing new flood defences, you may well see locals canoe down the street outside the bar you are stuck in.
Weather in Samui in December
December is the most popular month to visit Samui. The weather is agreeable and cooler and there is just a slight chance of afternoon showers. Expect crowds and high season hotel prices.