Best Time to Visit Koh Phangan and Koh Samui (and When Not To)

The best time to visit Koh Samui and Koh Phangan is February to March, the driest stretch on both islands: March brings 47 mm of rain on Samui and 41 mm on Phangan. Avoid October to December, when the Gulf gets its monsoon: November brings 457 mm on Samui and 433 mm on Phangan. July and August look dry in the totals, but the sky is nearly overcast, with rain on 7 to 8 days of 31 on Samui.

January is still wet on both islands (152 mm on Samui, 154 mm on Phangan), even though most guides count it in a dry season from January to April.

Where to be next: your month-by-month route, $19

A route for your months with a leave-by date for each stop, a backup, and the seasonal traps on your path. Drafted from 11 years of weather data, every number checked against it, in your inbox within 48 hours. Not included: visas, insurance or bookings.

See a sample plan Get my plan, $19

When is the best time to go to Koh Samui and Koh Phangan?

February and March. Here is Samui's year, which the other island follows closely:

Koh Samui: Average high and low temperature, °C

Koh Samui: Rainfall, mm

Averages 2015-2025 · Source: Open-Meteo, CHIRPS · How we measure

Read the rain line: a dry stretch from February to April, a lower hump from May to September, and the big peak from October to December that tops out in November. Cloud falls to about half the sky in February and March, and rain falls on only 2 to 4 days of 28 to 31, so what February brings comes in a few bursts, not spread across the month. Highs are 28° to 30°, warm without the heat of April and May. For one month at a time, see the Koh Samui and Koh Phangan pages.

How wet are October and November really?

They are the wet season, and November is its peak by a wide margin: 260 mm in October and 457 mm in November on Samui, 286 mm and 433 mm on Phangan. December is still wet (318 mm and 286 mm), though rain falls on far fewer days. In October and November it rains on about 18 of 30 to 31 days on Samui, so this is not the pattern of a short afternoon shower. If you want to work from the islands in this window, plan for cloud and wind on most days and a good indoor workspace.

Both islands sit on the Gulf side of Thailand, which gets its heaviest rain late in the year, after the Andaman coast has begun to dry out. Our three coasts guide lays out the month-by-month swap.

Are July and August the second dry season?

Not really, and this is where many guides go wrong. The weather is warm, at 31° on Samui in both months. But cloud averages about 89 percent across both months, nearly an overcast sky from morning to night, and rain falls on about 8 days in July and 7 in August on Samui, about double the 2 to 4 days of February and March. Totals are not what sets these months apart: August has 75 mm on Samui, no wetter than February. The difference is that the rain comes on two to four times as many days, under a heavy sky. So it is a fair time for a beach month on Samui if you accept grey skies, and a poor one if you expect the clear, bright weather of February.

Is Koh Phangan wetter than Koh Samui?

On rain days, yes, from April to October; on totals the two islands are close and take turns. Phangan has rain on more days, with the biggest gaps in July (about 12 days against 8) and September (about 14 against 10). Samui is wetter at the peak, in November and December. Here are the two islands side by side in the months that decide the choice:

If rain days are your main worry, Samui is the safer pick from April to October. In November and December neither island is a good bet, and Phangan's slightly lower totals do not change that. In February or March either island works, and you can choose on the place, not the weather.

Is January a safe choice?

January is the shoulder, and a wetter one than its rain days suggest. Samui gets 152 mm and Phangan 154 mm, just over the line we call a wet month, but with rain on only about 5 and 4 of 31 days, so it comes as a few heavy days rather than a grey month. Highs are 28°, among the coolest of the year along with December. It is clearly better than December, with about half the rain, and the drying trend continues into February. If your dates are fixed and you cannot wait for February, January is a fair compromise.

Do not read this as a promise for a particular week. These are averages over eleven years, so any given January can be drier or wetter. They give the odds: January is a fair bet that improves through the month, February and March are the best odds you will get, and October and November are poor odds on both islands.

What would we do?

For a month of work with beach time, book February or March. If you must go in the second half of the year, choose June to August over September to November, and pick Samui over Phangan. December is still wet: January is the better start, and the February guide shows which places beat the Gulf islands for dry warm weather. To set Koh Phangan against the Andaman coast month by month, see Koh Lanta, Phuket, Krabi or Koh Phangan, December to March.