Koh Chang Guide

Koh Chang Weather Information

What is the weather on Koh Chang like?

This is by far the most common question that we are asked at the Koh Chang Guide.
It makes sense really – of course you want to know what kind of weather to expect on the dates that you are thinking of coming here.

And luckily it isn’t too hard to give an answer. So if you want a quick reply read below. We’ll break it down quickly into temperature and rainfall and then go into much more detail later on in case you are interested.

Question – Will it be warm on Koh Chang?

Answer – It is always warm on Koh Chang.

You might not be able to tell if there will be fierce sun, clouds or even rain but you can rest assured that tomorrow on Koh Chang, like every single day on Koh Chang, will be warm. The daily high temperature is typically 30 degrees Celsius although this can drop to 26-28 in “winter” which is in November-December and up to the high 30’s in the hot season of march and April. Admittedly some nights in “winter” the temperature can drop to 16 degrees or so but tiy’d hardly call that cold would you?

Question – Will it Rain on Koh Chang?

Answer  –  October to May: It is very unlikely to rain tomorrow

…and if it does it is likely to be a brief, maybe heavy, shower – followed by sunshine. Full days of rain at this time of year are very rare.

Answer  –  June – September: It might rain and it might not.

There are very many sunny days during the “rainy season”. And when it does rain it is often brief and very heavy. Days when it rains all day are rare, weeks even rarer. If you come to Koh Chang at this time of year expect some rain and some sunshine. You just can’t be sure which you’re going to get tomorrow.

That’s it – those are the simple answers –  hope they help!

…but it you have a little more time then read on below and we’ll give you a lot more detail on Thailand Weather and  Koh Chang weather systems, seasons and the factors that can cause changes from year to year.
Detailed Information on the weather in Koh Chang and Southeast Thailand.

And The Koh Chang Weather Forecast?

The Thai Meterological department does a decent job of predicting the Koh Chang weather on its Eastern Thailand Page.

A good detailed forecast is also available from Wunderground here. Keep in mind though that an 80% chance of rain tomorrow is NOT the same thing as it raining for 80% of the time tomorrow – might be just a quick shower.

The 3 Seasons of Koh Chang Weather

Koh Chang experiences three main annual seasons of weather. A cooler dry season that runs from (approximately!) November to December, a hot season from January to May and a rainy season from June to October.

The Cool Season on Koh Chang

Koh Chang’s Cool Season typically begins in late October/early November and lasts for a couple of months. This is the windiest time of the year as the prevailing winds shift and blow over the island from onshore Thailand (Why? – see the monsoon section below). These land-sourced winds are drier and cooler and stronger than the prevailing maritime winds. The wind usually blows stronger at night and drops off or stops completely in the day.

Humidity is at its lowest on the island and the skies are clear – all in all it’s a pretty great time for Koh Chang weather wise and the cooler evenings provide a nice respite from the heat of the sun.

The Hot Season on Koh Chang

The hot season begins around january and is signalled by the dropping off of the cool season winds. What happens then over the ensuing four or five months until the beginning of the monsoon in June is that it is sunny, still and increasingly hot. There isn’t a great deal of cloud cover so as the Northen Hemisphere moves into summer the increased heat provided by the sun makes temperatures get hotter and hotter. Rain is rare but not uncommon and typically takes teh form of short, localised heavy showers followed by more sunshine.

…Which as a visitor is probably what you’re looking for. Just be aware of the enrgy-sapping effects of the daytime sun, especially when it is coupled with high humidity. Use sunblock always and drink plenty of water. And if you’re planning anything energetic then do it in the morning or evening.

The Rainy Season: Monsoon on Koh Chang

The Southeast Asian Monsoon is one of the world’s largest and most dramatic weather systems. In the summer the Indian and East Asian land mass is hotter than the ocean to the south. This causes the air to heat and a large area of low pressure forms over the land. The air over the sea is relatively higher in pressure so warm wet air from the ocean flows over the land mass and causes rainfall – often a lot of rainfall.

In the winter the opposite occurs. Water heats much more slowly than land so it takes months and months for the sea to get to an average temperature that is greater than that of the land. But when this happens the air over the sea is at a lower pressure than that over the land and drier air is the result as the prevailing winds blow from the land out to the sea.

Online Weather Predictions and The Rainy Season
It’s easy to look at an online weather service and decide that the weather is going to be bad on Koh Chang. It seems that they predict thunderstorms every day for about five months of the year. This is highly misleading though. These storms, when they do occur are often very brief and often at night. I’m writing this on a beautiful sunny day in July. It’s been sunny all day for the last four days. I heard a thunderstorm during the night last night. But the online weather forecast tells me it’s rainy and stormy though and predicts the same for the next 8 days. But guess what? I’m here and they aren’t. So just make a little mental note not to set too much store by these gloomy predictions – they just don’t represent the truth
But if you really want to check the online weather forecast here it is!

Effect of the Sea on Koh Chang Weather

Koh Chang has a maritime climate – that means that it is influenced by the sea. Not surprising really – after all it is an island. The sea has a moderating influence on temperatures. So when the temperatures are high in Thailand they are slightly less high in Koh Chang than somewhere far inland like Chiang Mai. And the same is the case when temperatures are cooler. The cool season is much warmer in Koh Chang than it is in the north of Thailand.

Effect of Koh Chang’s Hills on Koh Chang Weather

Koh Chang is a very hilly island and this can lead to very localised weather conditions – especially during the monsoon season. As warm sea air rises over the island’s jungly peaks it cools, and as it cools its capacity to carry water decreases. So what happens to the extra water? It falls as rain. This can result in sudden showers in a meteorological effect that is known as relief or orographic rainfall. Often the effect is very localised so you can encounter a sudden downpour from one small cloud that just covers an area of a few hundred metres and the next beach may be totally dry and sunny. it keeps life interesting!

Big Weather – El Nino and La Nina

El Nino and La Nina refer to a cycle of temperature fluctuations in waters of the Pacific Ocean. In El Nino years the waters of the Eastern Pacific Ocean are warmer than normal and waters in the western pacific are cooler than normal.I n La Nina years this is reversed and the Eastern Pacific is cooler and the Western pacific warmer than normal.

So how does El Nino affect Koh Chang? High pressure and therefore moisture follow hot water so in El Nino years the relatively cooler waters around Thailand and Southeast asia can result in droughts and lower overall rainfall. Similarlt La Nina years – which generally follow on from El Nino ones cause higher rainfall in the Thailand in Koh Chang.

Global Warming and Koh Chang?

The Earth is getting warmer due to the influence of mankind. This isn’t open to debate unless you own an oil company or are spectacularly poorly informed, living in a cave or, well, just pretty dumb.
It’s hard to gauge how this is affecting the weather in Koh Chang though. It feels like things are a bit more mixed up than before but maybe that’s just subjective. Here’s a quick summary of the last couple of years to give you a feeling for how unpredictable things are.

2015 – Winter and the hot season were fairly typical but very low rain in the monsoon which didn’t get going properly until September which saw massively heavy rain.

2016 – The cool season occured late and was much cooler than usual and also ran long until mid-March. Then it got crazy hot fast and a drought ensued all over Thailand. Daily highs in May were in the high 30’s in Koh Chang. Then in June it RAINED. The heaviest and wettest start to the monsoon in years. Now – July – we are back to the on-off sunny/showery days that are typical of the monsoon.

Koh Chang Weather Photos – The Good, The Bad & The Ugly


Posted on June 14, 2016 in Information Pages, Koh Chang NewsComments Off

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