The climate in Thailand is mainly tropical with high levels of humidity. The country is located within a monsoon region and temperatures are relatively high all year round, although generally the months of April and May have the highest temperatures. The winter months are the driest.

There are three seasons in the Thailand climate year. The monsoon season begins in June and runs until the end of October. Rain showers can be extremely heavy and last for hours, although some areas will see little rainfall before September. Flash floods are common at this time. In winter the temperatures are fairly low if you are in the mountainous areas of the country and at night can be as low at 2°C. Temperatures from November to February are a little more bearable than in summer and levels of humidity drop at this time too. This is helped by cooler winds which come in from the North East. Summer is from March to May and the temperatures in some areas of the country can rise as high as 35°C.

Recommended clothing for most areas for most of the year is light clothing although warmer items are needed in winter. Cotton is a recommended fabric as it allows air to the skin. Jackets are only recommended if you are travelling to northern areas during the winter months. Humidity can be as high as 75% in southern parts of the country and levels of more than this have been recorded in resorts such as Phuket.

Temperature ranges for different areas vary. In the Bangkok area the average temperature is around 26°C in winter and up to 30°C in summer. The area has its highest rainfall in September with an average of 320mm of rain. In Chiang Mai the temperature can be as low as 20°C or less during the winter months but there is a high of 29°C in the summer. The rainfall is highest in September with an average of 250mm.

In Pattaya the average winter temperature is around 26°C and in summer there is a high of around 30°C. The average rainfall there is highest in September with around 300mm of rain. In Krabi the winter temperatures are a little higher with an average of 27 or 28°C and rising to 29°C in summer. There is a very high level of rainfall in September with more than 400mm on average each year. In Ko Samui the average winter temperature is 25°C and in summer the average temperature is 29°C. The average rainfall is highest in November in this region with more than 300mm expected each year. In the popular holiday resort of Phuket the temperatures are also steady all year round with an average winter temperature of 27°C and a summer temperature of 29°C. September sees the highest amount of rain with levels of more than 400mm each year.

It depends on the time of year but in many of the areas already named temperatures range from around 12°C to the mid 20s at night time, so there are times when it can be uncomfortably warm in the evening. It is very rare for Thailand – and unheard of in many parts of the country – to experience frost or snow. The mountains have the lowest temperatures but even these rarely fall below freezing.

Parts of Thailand do experience plenty of sunshine and this tends to be higher during the winter months than during the summer. In January Bangkok will have on average more than 270 hours of sunshine, while in May it is below 250 hours. The levels drop to 150 hours during September but rise again towards the end of the year. Sunshine levels are naturally lower during the monsoon season due to increased cloud coverage but during the winter months and parts of the summer there is plenty of sunshine in the south of the country.

The flooding and heavy rain are usually as extreme as it gets in Thailand for the weather, although it was affected badly by the 2004 Tsunami and thousands in the region died, although this was a rare case. The country is not susceptible to hurricanes but there are earthquakes and some of those that have occurred in recent years have been very strong.