Weather on Koh Samui – When Is the Best Time to Travel
Koh Samui weather is really pleasant most of the time. The climate in Samui comes in three distinct seasons: dry, hot and rainy. Thailand lies between the Tropic of Cancer and the Equator (slightly closer to the latter). This makes its climate warm and humid all year round. The humidity level stands between 70 and 85 percent, and the temperatures averages at around 28°C. Koh Samui offers all that vacationers from cooler temperate countries could dream of regarding weather conditions. They are generally good year round, and the one thing you will rarely feel here is cold. You can enjoy the optimum weather conditions in Koh Samui between December and August.
The weather in Samui in January is excellent, making it a generally safe time to visit and be assured of hot and sunny days. The tail-end of the rainy season throws down only 90mm of rainfall, mostly delivered over seven days during the first half of the month. This is usually in short, heavy showers, often in the evenings or at night, leaving the days more often than not dry and cloudless. The average air temperatures are at their lowest at just 26°C/79°F, though the high humidity of between 67% and 92% will make it feel hotter, with only a slight breeze from the southeast to provide some cooling relief. Water temperatures are also around 26°C/79°F and the sea is extremely calm, making great conditions for diving and snorkeling.
The weather in Samui in February is probably the best in terms of living the tropical island life. A mere 30mm of rainfall is expected to fall in the evenings or nights of just five days, leaving the days sunny and dry and average temperatures at around 27°C/81°F. Humidity is also low and continuing to get even lower, averaging between 63% and 90%. The sea is great for divers and snorkelers, being perfectly calm and pleasantly warm at 27°C/81°F. With such ideal beach conditions, February is naturally quite a popular month for visitors, making this firmly a part of the high season. The Chinese New Year period is particularly busy, especially at the island’s shrines and temples.
The weather in Samui in March is fantastic if a little hot. The average air temperature is a scorching 29°C/83°F, with the average humidity of 63% to 91% rising as the month goes on and only gentle breezes from the southeast to cool you. The sea temperatures are also quite warm at 27°C/81°F, while the pancake-flat surface conditions and excellent underwater visibility make this the start of the peak diving and snorkeling season, with the chances of seeing whale sharks being relatively high. The chances of rainfall, in contrast, are quite low, with an average of just 30mm of rain expected over just four days of the month, usually around dusk or at night, which can make for really striking sunsets.
The weather in Samui in April is so hot that a thorough soaking during Songkran comes as a blessed relief! Naturally, the 29°C/83°F temperatures with a mere 80mm of rainfall expected over five days of the month (usually in the evenings or at night) make it one of the more popular times to visit the island paradise. A number of other big events take advantage of the great weather, including the LGBT Pride Festival and the Koh Samui Triathlon. On the beach, the water is barely ruffled by gentle south-easterly breezes and is about 28°C/82°F, with great visibility and interesting sea life for scuba divers and snorkelers to keep an eye out for.
The weather in Samui in May is as hot as it gets, with temperatures at an average of 30°C/85°F and hitting daily highs over 34°C/93°F. At the same time, an increase in rainfall – up to about 160mm dropping over nine days – leads to higher humidity, with daily averages between 62% and 92%. So long as you’re happy with the heat, though, the weather is generally good, with plenty of sunshine. Conditions on the water slowly started to deteriorate towards the end of the month, with the wind now coming from the west and waves picking up enough that diving and snorkeling become less practical on the west coast (but definitely still possible on the east coast). The sailing season now starts, and it comes in with a bang as the Samui Regatta dominates the final week of the month. Water temperatures remain at their hot season high of 28°C/82°F.
The weather in Samui in June is fantastic, providing the island with a mid-year mini high season. The anticipated 100mm of rainfall is less than both May and July and it is usually delivered in short, heavy deluges across about nine days as opposed to the lighter but more persistent rainfall of other times of the year. This leaves plenty of time in between to enjoy the longest days of the year, with 29°C/83°F temperatures and a declining relative humidity between 61% and 90%. The brief but powerful storms brought by the westerly winds obviously bring unsettled sea conditions with them, particularly along the west coast. While diving is still pretty good in the 28°C/82°F waters of the east coast, the other side of the island is best enjoyed by sailors and surfers.
The weather in Samui in July is generally very good. Temperatures are still high, at an average of 29°C/83°F, while humidity is at a comfortable average of between 61% and 89%. You are likely to get a few more cloudy days, with some afternoon rain showers on about nine days dropping the 120mm average rainfall. They are usually gentle and short-lived, making them nothing much to worry about. Sea conditions are also good, with the water temperature around 28°C/82°F and westerly winds providing good sailing and surfing on the west coast while the sheltered east coast still enjoys good swimming, snorkeling, and diving opportunities.
The weather in Samui in August is, for the most part, pretty good, though will need to be prepared for a little rain – as many as 10 days will see at least a light afternoon shower dropping part of the 100mm of expected precipitation. Making sure that you look up a few good indoor activities to keep you occupied will ensure that none of your holiday time is wasted. However, most August days are long and generally sunny, with 29°C/83°F temperatures and a comfortable level of humidity between 61% and 88%. The wind is mostly from the west and stirs up a few waves on that side of Samui, making it good for sailing. The popular east-coast resort towns still enjoy placid 28°C/82°F seas; perfect for swimming with young ones on their summer holidays.
The weather in Samui in September is starting to get cooler as we enter the autumn and winter months. Average temperatures are still quite pleasant at 28°C/82°F and the average humidity is between 63% and 89%. Rainfall is a feature of about 11 days of the month, though generally only in light showers adding up to about 130mm of precipitation. Most days are generally fine, with the added bonus that, after the August school holiday crowds, you can generally enjoy quiet beaches and attractions. Diving conditions are very good, with the clear water full of exciting marine life, average water temperatures of 28°C/82°F, mostly calm surface conditions on the east coast and noticeably smaller crowds at the more popular dive sites. With the wind coming from the west, the sea on that side of the island gets a little more ruffled, making it more popular with sailing enthusiasts. However, this is the last month of the sailing season before boat owners batten down the hatches for the coming monsoon season.
The weather in Samui in October is noticeably cooler and wetter as the monsoon season approaches. Monthly rainfall jumps up to 290mm, with 16 days disrupted by showers while most of the other 15 days tend to be at least cloudy. That’s not to say that sunny days are unheard of and it is entirely possible to have a very pleasant stay, with temperatures at 27°C/81°F and humidity between 65% and 93%. If you are looking for a beach holiday in Samui, October’s weather is a bit of a gamble, balancing the reduced hotel and flight prices against the risk of rain, making it advisable to have a few rainy-day activities lined up, just in case. Surfers, on the other hand, have absolutely nothing to worry about as the surfing season is just getting started. Water temperatures are at about 27°C/81°F while the changing wind direction – now coming mostly from the northwest – brings bigger waves.
The weather in Samui in November is best enjoyed by surfers. This is the peak season for wave riders, with the 27°C/81°F seas seeing meter-high breaks off most of the popular beaches, created by strong northerly winds. This makes celebrating Loy Krathong quite an adventure, to say the least! Enjoying a beach holiday is still possible as there are some sunny days, particularly early in the month. Temperatures are at quite a pleasant 27°C/81°F and humidity is around 70% to 94%. Furthermore, this being the low season, hotels and flights are at their cheapest. However, the risk of rain is at its highest during November, with 430mm of rain expected across 15 days, often in very heavy monsoon storms.
The weather in Samui in December sees a rapid return to blue skies and sunshine after the extremes of November’s monsoon rains. There will still be some rainy days, particularly early in the month, but you can expect only 150mm of precipitation dropped over nine days. Temperatures remain at their winter lows of about 27°C/81°F and humidity is steady at 68% to 92%. Surfers can still enjoy good waves as the northerly winds stir up the 27°C/81°F seas. However, by about Christmas time and in the run-up to the New Year celebrations, you will generally find ideal beach weather across the island.