Photo: Sirikwan Leechotjaruwong via Google
The verdict
- Best forTravellers who want calm, clear west coast water, reliable sun and big sunsets, and who can plan around the long monsoon
- Top pickNovember to February is the sweet stretch, dry and pleasant with calm seas, with December and January the festive but crowded peak
- One thing to knowThe green season from May to October brings heavy monsoon rain, rougher seas and some closures, so swimming is far less reliable then
Published 26 January 2026. Last reviewed 12 February 2026
Koh Chang runs on a clear tropical rhythm of two seasons, and the difference between them is sharper here than on the calmer gulf islands. The dry season from November to April brings the calm, clear water and the reliable sun, and the green season from May to October brings the southwest monsoon, with heavy rain, rougher seas and a much quieter, cheaper island. The air stays hot and humid all year and the sea stays warm, so the real question is not temperature but water and weather.
The thing to plan around here is the monsoon and the west coast. Almost everything you come for, the sandy swimming, the snorkelling and the famous sunsets, sits on the sunset facing west coast, and that coast is exposed to the monsoon swell. In the dry season it is calm and clear, in the wet season it turns choppy and cloudy with more jellyfish about, so the month you choose shapes how good the swimming and the sunsets will be, not just whether it rains.
If you take one line from this page, take this. Aim for the dry season from November to April for calm clear seas and big sunsets, accept the December and January holiday weeks only if you do not mind crowds and higher prices, and treat the green season from May to October as a green, quiet, cheaper trip for flexible travellers rather than a fixed beach holiday. Whatever the month, read the sea and the flags before you swim, since lifeguards are few or none.
Month by month at a glance
| Month | Air | Sea | Rain | Crowd | Verdict |
|---|---|---|---|---|---|
| January | Hot, around 31C | Warm and calm | Very low | Peak | Prime dry season, calm clear seas, busiest |
| February | Hot, around 32C | Warm and calm | Low | High | Dry, calm and clear, one of the best |
| March | Hot, around 33C | Warm and clear | Low | Moderate | Hot and dry, sea still calm and clear |
| April | Very hot, around 34C | Very warm | Building | Moderate | Hottest and humid, Songkran, dry ending |
| May | Hot, around 32C | Warming, choppy | High | Low | Monsoon arrives, seas turning rough |
| June | Hot, around 31C | Warm, choppy | High | Low | Wet and quiet, green and cheap |
| July | Hot, around 30C | Warm, rough | Very high | Very low | Heavy monsoon, rough cloudy seas |
| August | Hot, around 30C | Warm, rough | Very high | Very low | Wettest weeks, some closures |
| September | Hot, around 30C | Warm, rough | Very high | Very low | Still very wet, quietest of all |
| October | Hot, around 30C | Warm, settling | High, easing | Low | Rain easing late, season turning |
| November | Hot, around 30C | Warm, calming | Moderate, falling | Moderate | Dry season returns, fresh and green |
| December | Warm, around 30C | Warm and calm | Low | Peak | Peak dry season, calm seas, festive |
When each month earns its place
November. The turn of the season and a lovely time to come. The monsoon is bowing out, the seas are settling back toward calm and clear, and the island is at its greenest and freshest after the rains, with the waterfalls still full. Crowds are moderate before the December rush and prices are gentler, so the early dry season weeks are a quietly excellent window if you want the good water without the holiday crush.
December and January. The peak of the dry season and the busiest weeks of the year. The west coast water is calm and clear, the skies are reliable, the sunsets are at their best and the festive holidays fill the island with Thai and international visitors. Expect the highest prices and the fullest ferries and bars, especially over the New Year, and book accommodation and transport well ahead. This is Koh Chang at its liveliest and most beautiful, if you accept the crowds.
February and March. For many the sweet spot of the year. The holiday crowds have thinned, the weather is still dry and hot, and the sea stays calm and clear for swimming and snorkelling, with March heating up as the dry season matures. These are the months for the best balance of fine water, good sunsets and breathing room, before the building heat and humidity of April.
April. The hottest and most humid month, the dry season going out in a blaze before the rains. The sea is very warm and usually still calm early in the month, and the Thai New Year, Songkran, in mid April brings lively water festival celebrations across the island. The heat can be heavy, so plan shade and early swims, and watch for the first monsoon clouds building toward the month's end.
July to September. The depth of the green season, wet, quiet and cheap. The southwest monsoon brings heavy bursts of rain, rough and cloudy seas on the exposed west coast, more jellyfish and some smaller places closing for the low season. The upside is a lush green island, full waterfalls and very few other visitors, so it suits flexible, budget minded travellers who want nature and quiet over reliable beach days. Read the sea carefully before any swim.
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Before you go
What is the best time to visit Koh Chang?
The dry season from November to April is the best time, with calm clear seas on the sunset facing west coast, reliable sun and the big skies the island is loved for. December to February is the prime stretch, dry and pleasant, while the December and January holidays are the busiest and priciest weeks. The green season from May to October is cheaper and quieter but wet, with rougher seas.
When is the sea calm and clear enough for swimming in Koh Chang?
The west coast water is at its calmest and clearest through the dry season from roughly November to April, when swimming and snorkelling are at their best. The sea stays warm all year, around 27 to 30 degrees, but in the green season the southwest monsoon brings choppy, cloudy water and more jellyfish, so swimming is less reliable. Conditions are typical and never guaranteed, so read the sea and the flags.
Is it worth visiting Koh Chang in the rainy green season?
It can be, if you accept the trade. From May to October the island is at its greenest, quietest and cheapest, the waterfalls are full and the jungle is lush, and the rain often comes in heavy bursts rather than all day. The downsides are rougher cloudier seas, less reliable swimming, more jellyfish and some closures, so it suits flexible travellers more than a fixed beach holiday.
Which months are the most crowded and expensive in Koh Chang?
The peak is the December and January holiday weeks, when Thai and international visitors fill the west coast and prices and ferries are at their busiest. February and the rest of the dry season stay popular but calmer. For dry season weather with more room and lower prices, aim for November or late in the dry season, and the green season is quietest of all.
Do the ferries to Koh Chang run all year?
Yes, the car ferries from the piers near Laem Ngop in Trat run year round, including through the green season, since the crossing is short and sheltered. Service is most frequent in the busy dry season and the holiday weeks. Sea conditions on the open west coast are rougher in the monsoon, but the ferry route itself keeps running. Timetables are set by the operators and to be confirmed.
When are the Koh Chang sunsets best?
The west coast faces the sunset all year, but the dry season from November to April gives the clearest skies and the most reliable big evenings, especially from Kai Bae and the Bang Bao pier. In the green season clouds and rain can hide the sun, though a clearing monsoon sky can be dramatic. Time a late afternoon drink on the west coast for the best chance, conditions allowing.