What to expect, weather-wise, from your visit to Koh Chang
Koh Chang lies 10 degrees north of the equator, so is certainly a tropical destination. All year round, it is hot, in fact there's not much variation in the temperature, month by month, though some Thais might reckon that November is quite "cold" in Koh Chang.
South East Asia is generally assumed to have 3 seasons - November to February being the cool season, when monsoon winds come down from the North (but generally without rain) - March to May being the Hot Season (the period between the two monsoon seasons) - and June to September being the Rainy Season, when rains can come in periodically from the direction of the Indian Sub-continent. This generalisation is not a lot of help to the would-be traveler to Koh Chang.
As far as Koh Chang goes, it's probably best to give a month by month break-down of what sort of weather to expect on Koh Chang.
January. One of the best months of the year for sun worshippers to come to visit Koh Chang. The sun should be out every day, the air will not be too humid, and there is very little chance of any rain. The winds of early December are well past, and sea conditions should be calm, with good visibility for diving and snorkeling. Cool enough at night-time to forego air-conditioning. Downside? The waterfalls may not be too spectacular during this month.
February. Again, one of the best months of the year for beach loving folks to come to visit Koh Chang. Good hot sunshine on most days, though towards the end of the month there's a build up of more cloudy conditions, with the possibility of some rain, either very light, or short lived. Light winds, if any, and sea conditions should be calm, with good visibility for diving and snorkeling. Still no need for air-conditioning during the night. Koh Chang's waterfalls will be even drier this month.
March. Again, a good month to visit Koh Chang. Still lots of sunshine, though some days will be overcast, and the chance of some prolonged rain is increasing. When it is sunny, then it will be quite a bit hotter than it was in January, and quite humid too. Still not too windy, and sea conditions should be good with continued excellent visibility for snorkel trips. Becoming more humid at night, so an air-con bungalow becomes a good idea. Waterfalls maybe good, if your visit follows some recent heavy rain.
April. The time of the Thai New Year is associated with water as a cleansing agent, and during April the chance of rain increases day by day. There should still be plenty of sunshine during most of the month, but rain showers are likely in the afternoon and evenings. You'll still be able to find snorkeling boats, and on a good day you'll have calm seas and good visibility. April is statistically the hottest month of the year, and humidity can feel very high. Air-con is advised for a good night's sleep.
May. Can be very hot and humid, and there can be a lot of heavy rain in between the periods of good sunny weather. A good time to go trekking in the jungle, to try elephant trekking, or to visit waterfalls that can be spectacular between April and October. At this time, seas can become rough, both in the open sea and close to shore, where rip-tides can be dangerous. Humidity is high at this time of year.
June. Statistically June is the second wettest month of the year in the Province of Trat (I don't have figures for Koh Chang in isolation). My personal recollection is in fact of some decent weather in the Junes that I have spent in Koh Chang. Definitely hot, humid and wet, but with sunny days also. Sea can be rough, waterfalls can be splendid.
July. Similar to June. Koh Chang at its greenest, July is a good time for waterfall visits and jungle trekking. Seas can be rough, and during this period, it should be noted that the mainland ferry can be disrupted, so access to and from Koh Chang can be at risk. More so, the islands to the South of Koh Chang (Koh's Wai, Mak, and Kood).
August. Statistically the wettest month of the year with an average monthly rainfall of over 1,000mm (in Trat Province). A popular time, despite that, as it's the European school vacation period. Sunny days still occur in this month, and it does NOT rain all of the time!
September. According to records, about half the rain in September as in August. But, at the time of writing I have vivid memory of September 2009 being very very wet. I had written earlier of memories of good Septembers. It just goes to show, the weather of Koh Chang is anything but predictable.
October. Rainfall definitely down in October, and there will be long sunny periods too. This is the first month of the "high season" (a tourism term, not climatic). Towards the end of the month, the weather is generally very good. Winds can be strong overnight and in the early morning, and this can jeopardize boating activities. Becoming cooler in the evenings and overnight.
November. A great time to visit Koh Chang. The marine activities are getting into full swing and the daytime weather is sunny, dry and not too humid. It can be very windy overnight and early in the morning.
December. Middle of the high season. Great sunny weather, not too humid, high winds of November should diminish by the first week of the month. Quite cool at night, so no need for an air-con bungalow. One of the best months for sea-borne activities and for relaxing on the beach. Waterfalls are still good to see at this time of year. Should be no rain from December until the end of February.
You can read all of our daily weather reports here. Our main weather forecast page and live report is here, and our archive of weather images is here. Being a huge rock in the sea, a few KM from the mainland, Koh Changs' weather can change very quickly, and a good day in Chai Chet might be a lousy day in Bang Bao. From our sunny spot in Chai Chet, we can often see (and hear) grey skies and rain on the opposite side of Klong Prao bay.
No weather guarantee whatsoever is implied by the contents of this page, nor indeed by the entire website! Past (weather) performance is no guarantee of future performance!