Weather Thailand – Monsoon Seasons

Thailand weather has high temperatures and humidity levels are experienced throughout the year. The weather in Thailand is affected by two monsoon seasons:

  • South-West Monsoon – May to October effecting the West coast (Phuket and Khao Lak/Similan Islands)
  • North-East Monsoon – November to March effecting the East coast (Koh Tao, Koh Samui)
Monsoon Season Thailand
Monsoon Season Thailand

The Monsoon brings about routine flooding in the north, north-east and central regions, often causing mudslides and flash floods; visitors planning to trek in the jungle during this time should check conditions with licensed tour guides before leaving. Phuket can have flooding but that’s most of the time temporarily and does not affect tourism and divers.

The cool season, the favoured weather Thailand for most visitors, runs from November to February. Bangkok has a hot, tropical climate with daytime temperature reaching the mid-30s Celsius throughout the year. November to February is the driest time of year and the most popular with tourists. March, April and May are the hottest months, and the rainy season runs from May to October, of which October is the wettest.

Temperatures in the capital, Bangkok, range between 68°F (20°C) in December and 95°F (35°C) in April. January and February are normally dry, March to May is the hottest time of year, June to October tends to be the wettest season (with 90% of the country’s rainfall occurring in this period), and November and December are the coolest months.

As the rest of the planet, the weather is definitely changing over time. The seasons are not as clear as they used to be. For sure the hottest time is still the same, from March-May. And no matter if its raining or not, Thailand is still one of the better countries to spend your holidays in and rain or no rain, you can dive in Thailand 365 days a year with an average temperature of 27 Celsius.

Thailand can best be described as tropical and humid for the majority of the country during most of the year. The area of Thailand north of Bangkok has a climate determined by three seasons while the southern peninsular region of Thailand has only two.

Monsoon Thailand
Possible strong winds in low season

In northern Thailand the seasons are clearly defined. Between November and May the weather is mostly dry, however this is broken up into the periods November to February and March to May. The later of these two periods has the higher relative temperatures as although the northeast monsoon does not directly affect the northern area of Thailand, it does cause cooling breezes from November to February.

The other northern season is from May to November and is dominated by the southwest monsoon, during which time rainfall in the north is at its heaviest.

The southern region of Thailand really has only two seasons — the wet and the dry. These seasons do not run at the same time on both the east and west side of the peninsula. On the west coast the southwest monsoon brings rain and often heavy storms from April through to October, while on the east coast the most rain falls between September and December.

Overall the southern parts of Thailand get by far the most rain, with around 2,400 millimetres every year, compared with the central and northern regions of Thailand, both of which get around 1,400 millimetres.


So when is the best time to visit Thailand?

Generally speaking, the best time to visit Thailand is from November to February when the northeast monsoon is blowing cool, dry air that serves as a respite from the heat. During this cool season, the temperature ranges from 18 to 32 degrees Celsius in Bangkok, while in northern and northeast Thailand, temperatures can get quite cool with morning temperatures as low as eight to 12 degrees Celsius with the occasional 20 degree day. Nights can be particularly chilly and at high altitudes the temperatures can and do drop below freezing.

In Phuket we are quite lucky as we are able to dive 365 days in the year, compared to Khao Lak or Koh Lanta and Krabi for example who close down for the Monsoon season.

The summer period, or hot and dry season, is from March to June. At this time temperatures in Bangkok average around 34 degrees, but can often reach 40 degrees with humidity levels of 75%.

Try and avoid April if you don’t like it hot, unless you plan to be permanently submerged in the ocean, because this is the hottest month across the country. This is the best month for the Thai people as its their New Years celebration SONG KRAN. This is done with water pistols and water buckets the whole day long. Some places even celebrate this for a week.

From July to October is the monsoon, when most of Thailand’s annual rainfall is accumulated and flooding can ravage the country. The humidity averages just under 90%, with temperatures averaging around 29 degrees Celsius in a very wet and rainy Bangkok.

The monsoon finishes when the wind direction changes, bringing dry weather from the northeast. At best this season can be described as unpredictable and not the constant downpour of rain like you may expect. The middle months of this season may hold particularly heavy rains for the north of the country.