What uis the weather like on Koh Chang? Forecast and climate information.

Koh Chang Weather. The Climate and Seasons on the Island.

What is the weather like on Koh Chang?

Statistically, the weather and climate on Koh Chang can be summed up as:

  • The driest months are from November to March. This is High Season and is the best time to visit Koh Chang.
  • On average, the temperatures are always high i.e. over 30C during the daytime year round
  • March and April are the hottest months on Koh Chang
  • January is the coolest month
  • January is also the driest month of the year
  • September usually has the worst weather
  • The rainy season is from May to October
  • The air quality can be poor in January & February (AQI of 100 – 200 is possible on certain days)

The weather on Koh Chang in January.

The weather on Koh Chang in January is usually sunny.  Visitors can expect an average of 9 hours sunshine per day. With average high temperatures of 31C and night time lows of 20C.  January is a dry month with an average of 3 days with some light rain, around 20mm or so.  The average sea temperature in January is 27C.

The weather on Koh Chang in February.

The weather on Koh Chang in February is usually sunny.  Visitors can expect an average of 9 hours sunshine per day. With average high temperatures of 33C and night time lows of 21C.  February is a dry month with an average of 5 days with some light rain, around 50mm or so.  The average sea temperature in February is 28C.

The weather on Koh Chang in March.

The weather on Koh Chang in March is usually sunny but expect a day or two with a rain shower.  Visitors can expect an average of 9 hours sunshine per day. With average high temperatures of 33C and night time lows of 23C.  March is quite a dry month with an average of 7 days with some light rain, around 90mm or so.  The average sea temperature in March is 29C.

The weather on Koh Chang in April.

The weather on Koh Chang in April is sunny but with some overnight thunderstorms.  But visitors can expect an average of 9 hours sunshine per day. With average high temperatures of 33C and night time lows of 24C. It can be very humid at night.  You will experience some rain in April. There’s an average of 9 days with rainfall. Around 120mm or so.  The average sea temperature in April is 30C.

The weather on Koh Chang in May.

May is the start of the rainy season, so the weather on Koh Chang in May will be much wetter than April.  Visitors can expect an average of 8 hours sunshine per day. With average high temperatures of 31C and night time lows of 24C.  The number of days with rain will outnumber dry days with an average of 20 days with rain and 350mm total rainfall.  The rainy season usually begins some time during the middle of May. The average sea temperature in May is 30C.

The weather on Koh Chang in June.

The weather on Koh Chang in June is usually quite wet, although visitors can expect around 7 hours of sunshine a day.  But skies are often cloudy. Average high temperatures of 30C and night time lows of 23C.  June is a wet month with an average of 23 days with some rain and a total of 550mm rainfall for the month.  Heavy rain is usually at night or very early morning, rather than during the day time. The average sea temperature in June is 29C.

The weather on Koh Chang in July.

The weather on Koh Chang in July is usually quite wet, although visitors can expect around 7 hours of sunshine a day.  But skies are often cloudy.  Average high temperatures of 30C and night time lows of 23C.  July is a wet month with an average of 21 days with some rain and a total of 550mm rainfall for the month.  Heavy rain is usually at night or very early morning, rather than during the day time. Afternoons and evenings are usually dry. The average sea temperature in July is 28C.

The weather on Koh Chang in August.

The weather on Koh Chang in August is very similar to July. With quite a lot of rain but around 7 hours of sunshine a day.  Average high temperatures of 30C and night time lows of 23C.  August is a wet month with an average of 23 days with some rain and a total of 550mm rainfall for the month.  Heavy rain is usually at night or very early morning, rather than during the day time. The average sea temperature in  August is 27C.

The weather on Koh Chang in September.

September usually has the worst weather of the year. There’s more chance of floods and storms than at any other time.  Although there are still plenty of sunny days and an average of 6 hours sunshine per day.  Average high temperatures of 29C and night time lows of 22C.  It rains on average on 22 days of the month during September, with a total of 550mm rainfall for the month.  Heavy rain is usually at night or very early morning, rather than during the day time. The average sea temperature in September is 27C.

The weather on Koh Chang in October.

The weather on Koh Chang in June is still wet but now improving as the rainy season comes to an end.  Expect around 7 hours of sunshine a day.  But skies are often cloudy. Average high temperatures of 30C and night time lows of 23C.  How wet October is varies quite a lot year by year. It depends when the rainy season ends.  Sometimes this is in the middle of the month, sometimes at the end or in early November. Figure on an average of 20 days with some rain and a total of 300mm rainfall for the month.  Heavy rain is usually at night or very early morning, rather than during the day time. The average sea temperature in October is 29C.

The weather on Koh Chang in November.

The weather on Koh Chang in November is usually sunny.  The prevailing winds change direction and blow from the north which signals the end of the rainy season. Visitors can expect an average of 9 hours sunshine per day. With average high temperatures of 30C and night time lows of 21C.  November is a often a very dry month with just a few rainy days and an average rainfall of 50mm.  The average sea temperature in November is 27C.

The weather on Koh Chang in December.

The weather on Koh Chang in December is usually sunny but cool in the evenings due to the north wind .  Visitors can expect an average of 9 hours sunshine per day. There may be some cloudier days due to tropical storms passing from the Philippines towards the south of Thailand. Koh Chang usually doesn’t get any rain from the storms, just some cloud for a day or two as the storm passes. Average high temperatures of 30C and night time lows of 20C.  December is a dry month with an average of 3 days with some light rain, around 30mm or so.  The average sea temperature in December is 27C. 

Today’s Weather Forecast for Koh Chang

 

When is the best time to visit Koh Chang?

The Seasons on Koh Chang

High Season

What to expect . . . High Season coincides with the best weather, so From mid-November through to  March you can expect plenty of sunshine and hardly any rain.  You’re 90% certain to have sunshine throughout your stay with just the occasional rain shower.   There should be a gentle sea breeze and blue skies.  The sea will be calm, and especially early in the High Season, will have very good visibility for diving and snorkeling. You can also expect some strong winds from the northeast in November & December which cool things down a little.  This is the time to visit if you’re planning on chartering a yacht.

The hottest time of the year in Thailand is from March to mid-May.  Whilst it isn’t as hot on Koh Chang as it is on the mainland in central and northern Thailand, it can still reach 36 – 38C.  Which is hot enough.  The sea also heats up considerably, so rather than cooling you off.  It can feel too warm.

Low Season

From mid-May through to October it’s the season referred to as one of the following: rainy season / green season / low season or simply the season to shelter indoors and play with your XBox for 5 months.   Whatever you call it, there will be rain most days.   However, this is often just in isolated showers during daylight hours.   Most of the heavy rain is overnight.   So you will see the sun, but can’t guarantee how much or on what days.

If you just want a quiet escape from everyone then June or September are ideal.   May & November are also often pretty good months for visiting as they often combine quite  a lot of sunshine with cheaper airfares, cheaper rooms in most resorts and relatively few visitors.  The sea can be very rough however during the rainy season.  Rip tides are common, so care is needed when swimming in the sea. Dive boats and snorkeling trips still run when the conditions are good, but usually not daily.  

Another reason to visit in the Low Season is that there can often be days when the weather is actually better than during the High Season.

For example, the photo on the top of the page with clear blue skies and a wide deserted beach was taken in mid-June.  Supposedly June is one of the worst months to visit.  The weather forecast shows rain every day.

But you won’t get that view in the High Season. The tides are higher, so you won’t ever see a 50 metre wide beach if you visit from December  to March.  And there are far, far more people at that time of year.  That’s White Sand beach in the photo.  It’s the busiest beach on the island.  But go to the beach any hot sunny day in June and you can easily count the number of people you see out on the sand. 

Air Quality and Air Pollution on Koh Chang.

In the High Season, from late December to March or even April, the sky is often hazy.  This isn’t a freak occurrence, it happens every year at the same time of year.  It is due to pollution.  Not from vehicles or construction, but from fires.  This is usually sugar cane farmers who set fire to the crops as it’s an easy way to remove leaves. 

Most of the smoke is coming from Cambodia which, thanks to EU subsidies has seen a huge increase in sugar can farming over the past few years. So, whilst you may think that putting biofuel in your car is saving the planet, but in reality it’s not so good for the environment in the areas where the sugar cane, the source of the ethanol, is grown. Due to farmers using the quickest and simplest way to harvest. 

If there are a lot of fires over the border in Cambodia and the wind is blowing from the East or Northeast, then the AQI (Air Quality Index) can get to 100  – 150 range.  This is classed as ‘Unhealthy for Sensitive Groups’.  Ideally you want to be somewhere in the 0 – 25 range.  Although in Thailand, the recommended healthy level is double this at 50.   On this scale, anything over 300 is classified as ‘Hazardous’ and you should stay indoors if possible.

February 2020 was particularly bad for air quality.  I now have my own AQI meter.  On clear days during the rainy season the reading is under 10.   A normal day during high season is around 30 – 50. 

But in February 2020 the fires in Cambodia, caused by farmers burning sugar cane, were worse than normal.  That plus a northeasterly wind caused the AQI to peak at around 300 for a few days.  At that level you can smell and taste smoke and inland mountains virtually disappear from view.  On some days Koh Chang itself wasn’t visible from the mainland.  Fortunately, that only lasted for a few days.

Global Forest Watch monitor major fires burning around the world, which are seen on satellite data, and their site provides real time information.  Click here to see the current situation in Thailand and Cambodia, then zoom out and compare to Europe.   Then you’ll realise why the sky is hazy.

This photo shows the difference.  A normal day vs a hazy day.  

Koh Chang Air Quality comparison

You probably won’t notice any smell or any difficulty breathing, unless you are very sensitive to smoggy air or have a respiratory illness.  The AQi has to be over 200 before you notice an obvious smokey smell in the air. But if you have an respiratory problems, then checking the AQI of any destinations in this part of the world, especially between January – March,  is worth doing before you plan a holiday.

Air Quality on Koh Chang: https://www.airvisual.com/thailand/trat/ko-chang-tai

The Climate on Koh Chang

In total Koh Chang receives around 3,000 – 4,000mm of rain each year, most of it falling in the rainy season. To put that in perspective, the north of England averages about 800 – 1,000mm of rain every year.   However, as I mentioned above, the rain is in heavy tropical downpours rather than drizzling for days as it does in the UK & northern Europe.

Trat province is one of the wettest areas in Thailand, but that doesn’t mean that it is constantly raining for six months of the year.

The majority or rainfall comes in the form of storms or very heavy rain showers which often last only 30 minutes per day before the sky clears and the sun comes out.   So having an entire week of grey, overcast sky and no sunshine is quite a rarity.  If you are visiting the island in the European summer holidays, you aren’t going to be able to guarantee that you’ll come home with a deep tan.

It’d be nice is there was an accurate Koh Chang weather forecast for the rainy season.  But, it’s very hard to say how a day will turn out.  That’s why pretty much every forecast you will see shows a 50% chance of rain, the possibility of a thunderstorm and the possibility of sunshine.  You’ll often get all of those in the same day with an overnight thunderstorm followed by a grey morning and clear and sunny afternoon.

Graph showing average rainfall for Koh Chang island, Thailand

Temperature: It’s around 28-30C every day.   A little warmer in March and April, possibly up to high 30’s C.   And in December the mercury will struggle to get to 27/28C during the daytime, before plummeting overnight to around 15-18C. (If you have never experienced a night at 15C, then believe me, it is cold.   You’ll need to pack a long sleeved shirt if you plan on going out on a midwinter’s evening.)

tempchart

Conditions at Sea:  During the High Season the sea is usually very calm.  In fact, in the mornings especially, it can be like a lake with barely a ripple.  However, there can be rip currents from May – October.  The waves are never huge, but as the beaches slope gently into the sea, this can cause rip currents to form in certain places on all the main beaches.  Every year several visitors drown.  There is one permanent lifeguard on duty outside KC Grande Resort on White Sand beach, but other than that, you’ll have to rely on help from fellow visitors or hotel staff if you get into difficulty.

Humidity: It’s a tropical island full of jungle and trees, so you’ll sweat a lot regardless of what time of year you visit.   That’s really all you need to know.

More Detailed Weather Forecasts

Koh Chang Weather Infographic