When is the best time to visit Koh Samui?
For great beach weather, less rain, and fewer crowds I like to visit Koh Samui between February and June. Of these months, February and March are the driest of the year while May and June might see a few showers, sometimes heavy showers. However, these months are great for sightseeing as well as getting discounts on planes and hotels.
- Best Time to Visit Koh Samui for Good Weather: Late December to April has great weather, little rain, and lots of sun. From May to September there’s still plenty of sun but you will get some rain – usually brief showers in the afternoon or night. October and November are the rainiest months when good beach weather can be hard to find.
- Best Time for Snorkeling, Scuba Diving, and Day Trips to Angthong Marine Park: Koh Samui is not known for its snorkeling or scuba diving but day trips to Koh Tao are popular. The best time for diving on Koh Tao is anytime outside of November and early December with March, April, and May the best months to see huge whalesharks. Kayaking trips to Angthong Marine Park are also a highlight of a trip to Koh Samui and they’re best from late December to September with the park being closed every year in November and early December.
- Best Time to Save Money: Visiting during the rainy months of October and November will certainly get you some great deals on hotels. While the weather can be stormy during this period sunny days are still possible. A better mix of good weather and prices is found during the months of April, May, and June. These months are hot and humid but very sunny and not a lot of tourists.
- High Season (late December, January, July and August): Great beach weather. Sunny and warm but not blazingly hot like April and May. Expect some rain but it usually passes quickly. Book the Best Koh Samui Hotels and the Best Koh Samui Family Hotels months in advance – especially for the weeks around Christmas and New Years.
- Shoulder Season (February, March, April, May, June, September, early December): Great beach weather with February and March being the 2 driest and sunniest months to visit Koh Samui.
- Low Season (October and November): The rainiest months of the year but it’s still possible to have a string of nice days.
Koh Samui Weather by Month
Temperature by Month (high in Celsius)
Rain by Month (mm)
- January Weather on Koh Samui: Great beach weather with lots of sun and little rain. (Average Max Temperature: 28°C. Average Rainfall: 40mm. Days with Rain: 7)
- February Weather on Koh Samui: Great beach weather. February and March are the sunniest and driest months on Koh Samui. (Average Max Temperature: 29°C. Average Rainfall: 10mm. Days with Rain: 5)
- March Weather on Koh Samui: Great beach weather with many dry sunny days. (Average Max Temperature: 31°C. Average Rainfall: 10mm. Days with Rain: 4)
- April Weather on Koh Samui: Great beach weather with lots of sun and little rain. (Average Max Temperature: 32°C. Average Rainfall: 70mm. Days with Rain: 5)
- May Weather on Koh Samui: Good beach weather. Sunny but more rain and humidity. (Average Max Temperature: 33°C. Average Rainfall: 180mm. Days with Rain: 9)
- June Weather on Koh Samui: Good beach weather. Hot, humid, and some rain. (Average Max Temperature: 32°C. Average Rainfall: 100mm. Days with Rain: 9)
- July Weather on Koh Samui: Good beach weather. Hot, humid, and some rain. (Average Max Temperature: 32°C. Average Rainfall: 130mm. Days with Rain: 10)
- August Weather on Koh Samui: Good beach weather. Hot, humid, and some rain. (Average Max Temperature: 32°C. Average Rainfall: 110mm. Days with Rain: 9)
- September Weather on Koh Samui: Good beach weather. Hot, humid, and some rain. (Average Max Temperature: 31°C. Average Rainfall: 190mm. Days with Rain: 11)
- October Weather on Koh Samui: Lots of rain but there will still be some sunny days. (Average Max Temperature: 29°C. Average Rainfall: 260mm. Days with Rain: 15)
- November Weather on Koh Samui: The rainiest month of the year. Lots of rain but nice beach weather is still possible. (Average Max Temperature: 28°C. Average Rainfall: 290mm. Days with Rain: 16)
- December Weather on Koh Samui: Good beach weather. Some rain at the beginning of the month but sunny dry days are the norm after December 20. (Average Max Temperature: 27°C. Average Rainfall: 90mm. Days with Rain: 8)
I'm Santorini Dave. I started this site in 2011 with a short article on tips for visiting Santorini with kids. We're now a small team of writers and researchers dedicated to providing the best travel content on the internet. We focus on 
Have booked for last week of November in Koh Samui. Posts are confusing. I’m expecting rains and sunny days too. Is it worth it? How have the past few years been in late November?
You should expect and prepare for everything. November weather can bring anything from storms and flooding to sunny clear days.
Hey Dave,
Loving your blog, good work!!
I have a question about what month to visit in, if I wanted beach weather would it be safer to travel in August or December?
Regards
Ryan
Tough one. Probably August but both are right on the fence between rainy and dry seasons. Be prepared for a bit of rain regardless of which one you choose. By late December weather is consistently pretty nice.
Hey there, we are going to Samui for Christmas. What’s the situation with mosquitoes at that time?
I’ve never had a problem with mosquitoes in Koh Samui at any time of year. Should be fine (though mosquito experiences do seem to vary greatly based on the person).
Hi Dave,
Thanks for the blog! So helpful. My girlfriend and I are planning on going there for the first two weeks of July. As far as I understand from your blog, the weather is actually quite good, however probably rain during the afternoon (a few hours a day?) but otherwise plenty of sun. Can you advise on the sea and whether it is the beautiful sea we see on pictures or if the wind is messing it up with dirt and such? And also, if there are (too) many tourists these weeks?
Thanks!
Thomas B
The weather can be uncertain (no guarantees) but in general should have plenty of sunny days. Rain at night or late afternoon. Sea is beautiful when the sun is out. It’s sort of a second peak season but not as busy as January/February.
I have just booked flights to Bangkok going in January. Just looked for connecting flights to Koh Samui with Bangkok Air but nothing available yet. Do you know how far in advance flights become available? Great blog by the way enjoyed reading it. Mandy Breen
Flights come online about 9 to 11 months in advance, so should be very soon.
Hi Dave,
I’m planning to visit Koh Samui this December between 15th to 21st. Looking forward to snorkeling. Is Ang Thong Marine Park open?
Ang Thong Marine Park is closed every year from November 1 to December 15 to allow nature some time to recover from tours and human interaction. This is also rainy season in the area and coincides with rough seasons and heavy rain so it would not be the best time to visit the park even if it was open. The re-open date can change a little every year so you should be OK but do check before arrival.
Hi Dave,
Thank you for the great blog – it’s been very helpful in planning our trip to Koh Samui. We will be there the last week of November. I am looking to hire a boat company to take us to Angthong Marine Park. One company says the park is closed for November, the other is offering to book the trip. From what I can find online, in prior years, it’s been hit or miss whether they close the park this time of year. 1. Do you know if the park will be closed for November? 2. Is there an alternate group of islands that is as spectacular for a day boat trip? 3. Do you think the seas will be too rough that time of year regardless?
Thank you!
Rich
It just depends on the weather and circumstances when you visit. I don’t think I would book in advance – just wait and see if they’re running. You could do a trip to Koh Tao if you were into snorkeling/diving but otherwise you should go to the west coast where there are many such day trips and the weather improves earlier than on the east coast.
Hey! I’m traveling to Koh Samui from 6-10 November. Do you think it would be raining throughout? Would we get some time to swim? Does it get sunny at all? I’ve travelled to Goa in July, which was the peak of monsoons but it wasn’t so bad though seas were a bit crazy. Let me know what you think. Seanie
This is the center of the rain season so yeah, expect rain. Will you get some sun and beach time? Probably, but there can be some substantial storms in between early October and mid-November so be prepared for anything. And after a big storm (regardless of the season) beaches can be littered with debris for a few days until the tide takes everything out.
We plan to go to Samui in the end of December. Some sites say the sea is too rough for water activities. What’s your experience?
Best,
Jay
You can still get a few gray days and rain in late December but the sea is generally calm and fine for swimming.
Hello, we are planning to go to Koh Samui in mid December with kids. Are there fun activities for 15 & 9 yrs old boys?
Vaishali Jain
Zip-lining, go-cart racing, and Chaweng water park (with huge inflatable bounce platforms floating in the ocean) would be my top recommendations.
Looking at revisiting Koh Samui in late October/early November is it worth the risk weather wise, visited in late May/early June and had great weather and time? I have been to Patong a few times would you suggest Patong Beach or should we try Khao lak instead.
Thanks
Dean
Late October, early November is the rainiest time on Koh Samui. You could still find some patches of sun and beach time but unless you’re happy cocooning with a book on your balcony and watching the rain come down (sometimes pretty great, actually) then I’d not risk it. (And yes, Khao Lak is much nicer than Patong.)
hi dave!
I hope you are well. I am planning a trip to thailand from the 10th to the 17th of September. I was wondering if it would be raining thoughout the day or if there are usually just showers here and there? Is that a good time to go to Thailand or do you recommend I travel elsewhere during that time of year?
thank you!
D.
There will be some rain, for sure, in mid September, but likely plenty of sun too. Phuket is usually wetter, Koh Samui should still be dryer in September. There certainly are places with more idyllic weather (e.g. Bali is wonderful in September).
Looking to book a honeymoon trip to Ko Samui and the lower gulf from November 18 to December 2. I keep reading that this is monsoon season but also hear that the rain comes and goes. Is this a bad time to visit?
Jennifer
This is the end of the monsoon seasons so yes, you can still get some grey skies and rain. But you can also get some beautiful days. Be prepared for a bit of everything. Hotel rates are still very cheap as the crowds don’t appear until mid-December.
Hey,
I have a question about traveling to Koh Samui in December. We are planning to travel to Koh Samui from December 8th to the 12th. I keep reading that this is still rainy season but would you be able to tell me what we could expect? It is usually full days of rain or is it an hour or two of rain and then it clears up?
Thanks for your help.
Cynthia
It’s rare that it rains non-stop, more like a few hours at a time. It can remain grey though for longer stretches. Early December is when it transitions from rainy to dry seasons and it can go either way. I still enjoy visiting then regardless, but just be prepared for at least a bit of rain – and probably some sun too.
Hi.
Where is the best hotel/beach to stay in Koh Samui in early May?
Best place to relax and calm waters without waves.
Carlos
Chaweng Noi or Choeng Mon.
Hello,
I am traveling from Utah to Koh Samui and Chiang Mai in April. I am wondering how safe it is in these areas? I have read some scary things (I know, you should never google) but how safe is it for Americans?
I consider both Koh Samui and Chiang Mai to be very safe. Car accidents are always the biggest risk to travelers. The two biggest things you can do to increase your safety is always wear a seat belt (it’s easy not to in foreign countries) and don’t ride a motorbike or scooter.
Hi Dave, is Dengue Fever present on Koh Samui?
Megan
Dengue is spread by mosquitoes and I’ve never had a problem with mosquitoes on Koh Samui. Dengue is not bad on Koh Samui but it is present. It’s worse during rainy season (October/November) but can occur any time. I recommend taking a good Deet repellent that you can use if there seems to be a lot of mosquitoes where you’re staying (as opposed to waiting until you’re there and then going to the local store and getting a lousy alternative). The Off! Deepwoods VIII mosquito repellent was rated the most effective Deet repellent by Consumer Reports.
Going to SE Asia for 1 month and want to spend 2 weeks on Koh Samui relaxing and beach time. We can either do it at the end of our trip or beginning. When would you recommend visiting Samui – late or early January – for the best beach weather? Thanks, Adam.
Both early and late January typically have good weather but it does tend to get better (or at least, is more consistently good) as the month goes on. So, if it makes no difference to your other plans then go with the end of the month.