The information below is simply a guide for you if you are planning a trip to Thailand. We think you might find it beneficial to see an overall picture of typical annual water patterns in Thailand by region to consider when making you travel plans.
Please note: that even during monsoon season and other times through the year, there are still a lot of activities, fun and exciting adventures to be had all throughout the country. There are festivals and celebrations on all year, and now that we are slowly all coming out of our caves post COVID, and being hidden away , we are ALL ready to seek some new adventures!
Thailand’s climate is tropical, with three separate seasons:
- a hotter season from March to mid-May;
- a significant rainfall caused by the south-west monsoon, which generally lasts from mid-May to October; and a cooler season from November to February.
- a drier and comparatively cool season from November to February, when the Asian continent’s north-east monsoon prevails. However, the relatively cool season is felt in the north and inland areas, while it is hot even in winter on the coasts and in the south.
The rainy season follows a different pattern in the southern peninsular region, where beaches and popular destinations can be found, than it does on the continent, as will be described later.
The map below shows Thailand and its provinces and cities
The average rainfall in Phuket is shown below: from December to March, rainfall falls below 100 mm (4 in) per month.
The following are the average temperatures in Phuket.
Since the winds blow from the shore, the temperatures in winter are slightly higher than on the east side (also described as, from the inland area of the peninsula).
The volume of sunlight on the western coast is quite minimal from May to October, whereas the sun shines consistently from January to March.
So, the great time to visit the western side is from late December to March; in April, pre-monsoon thunderstorms are more common than anywhere else.
The average rainfall in Ko Samui, an popular resort island in the Gulf of Thailand, is shown below.
As you can see, the rains are quite frequent in the summer but not particularly abundant, whereas they are definitely plentiful in October and November.
The rains can sometimes last until the beginning or middle of January, so the best time to visit this area, which also includes Pattani and Songkhla, is from the middle or end of January to April (with a preference for February, since here too March and April are a bit hot).
The following are the average temperatures on Ko Samui.
The northern part of Thailand
The climate is hot for most of the year in the northern inland plains and valleys of the north-western hilly area, except in winter, when it’s sunny during the day but a little cool at night, especially in December and January (and a little less in February), when night-time temperatures drop to around 16/17 °C (61/63 °F) in the centre and to 14/15 °C (57/59 °F) in the north.
Chiang Mai, Thailand
In December and January, when cold air masses from China arrive, the night temperature in northern cities such as Chiang Mai can drop to around 5 °C (41 °F), and in some cases even lower. However, by February, the daytime temperature begins to rise and frequently reaches 33/34 °C (91/93 °F), rising to 35/37 °C (95/99 °F) between March and May, with peaks exceeding 40 °C (104 °F).
Chiang Mai’s average temperatures are listed below.
Chiang Mai’s monsoon season lasts from mid-May to mid-October. The annual precipitation in the inland plain ranges between 1,000 and 1,500 millimetres (40 and 60 inches), with a similar pattern of scarce and rare rains from mid-November to April and heavy rains during the monsoon period, with a peak in the last part of the year (August and September). The average precipitation in Chiang Mai is shown below.
The amount of sunlight in Chiang Mai is very good during the dry season, from December to April, when clear skies prevail, but not so much during the monsoon season, from June to September, when there are several cloudy periods.
The best months to visit this area are December and January, because unless you are used to it, the heat can become uncomfortable in February, especially in the plain’s south-central region.
Bangkok and its environs
The weather in Bangkok’s capital is hot all year. The weather is generally pleasant between mid-November and January, with clear skies. Peaks are around 32 °C (90 °F) and declines are around 22 °C (72 °F), so even though it’s winter, it’s hot. Temperatures begin to rise in February, and the weather remains sunny, with the exception of a few brief thunderstorms.
Between March and mid-May, prior to the arrival of the monsoon, the heat becomes intense: highs can reach 37/38 °C (99/100 °F), and the temperature often remains around 28/29 °C (82/84 °F) at night.
The capital is not as hot as the north-central inland areas, but it is more humid as a result of its proximity to the sea; additionally, the heat is trapped within the city (an occurence referred to, as urban heat island effect.) There is no other option but to settle down in air-conditioned rooms.
The following are the average temperatures in Bangkok.
The monsoon arrives in mid-May, and the temperature begins to fall. The weather is frequently cloudy during this period, and the humidity rises even higher, but the rains, in the form of showers and thunderstorms, which can be quite intense, provide some relief. In any case, very hot days may still occur during the summer months, in the intervals between periods of bad weather.
The average annual rainfall is 1,450 mm (57 in); the highest rainfall months are September and October, at the conclusion of the monsoon season, with 345 mm and 240 mm (13.5 and 9.5 in) of rainfall, respectively.
The average precipitation is shown below.
The amount of sunshine in Bangkok is also very good during the dry season, from December to April, when the sky is usually clear, but not so much during the monsoon season, from June to September, when there are several cloudy periods.
From December to mid-February is the best time to visit Bangkok because it is the least hot and outside the rainy season.
Pattaya, located south-east of Bangkok, has a climate similar to that of the metropolis, but it is situated on a stretch of coast (which extends down to the Sattahip area) that is relatively protected from the downpours: an average of about 100 mm (4 in) of rain falls per month from June to August.
The average precipitation is shown below.
Needless to say, we’re still in a hot and humid summer season with little sun, and tropical storms and typhoons can disrupt the territory (see below). In essence, the weather from June to August isn’t ideal, but if you’re fortunate, it might be bearable. Pattaya’s wettest months are May, September, and October, which marks the start and completion of the rainy season. The best months to visit are December to February, with March and April remaining dry and sunny but a little hot (though not as hot as the inland).
The following are the average temperatures.
The coastline to the south-west of Bangkok, southward Ao Noi , is also relatively protected, with summer rainfall totalling only 1,000/1,200 mm (40/47 in).
The wet coast
Summer rains are more plentiful south of Pattaya, beginning with Rayong, and they are abundant in the easternmost portion (see Chanthaburi, Trat, and Koh Chang), where summer is generally not recommended. Rayong receives 1,700 mm (67 in) of rain per year, while Koh Samet receives 1,340 mm (53 in), and Chanthaburi receives up to 2,800 mm (110 in) and Trat receives up to 3,500 mm (138 in).
Nevertheless, the winter here is also dry and beautiful, and the best time to visit is from December to February; in March and April, the weather is warmer, but sunny, even the first short pre-monsoon rainfall.
The climate in Peninsular Thailand is hot all year. Because the rise in temperature between March and May is not as strong as in the mainland region, these months are only slightly warmer than the remainder of the year: highs are around 33/34 °C (91/93 °F) rather than 31/32 °C (88/90 °F), though it can get very hot here as well. Furthermore, the annual rainfall in the peninsular area take place at different times depending on the side.
Let’s see when that happens.
The summer monsoon is not especially heavy along the east coast, overlooking the Gulf of Thailand (or Gulf of Siam), from Chumphon to the Malaysian border, so much so that the area is popular with tourists during the summer, which is considered high season. On the contrary, the so-called retreating monsoon brings heavy rainfall, sometimes torrential, in the early months (October to December), when the sea is still warm and able to provide energy and moisture.
Regardless of the differences in rainfall patterns, the (relatively) cloudiest season on the east coast is also June-October, though there isn’t much more sun from November to January.
The sea in Ko Samui, and generally in Thailand, is pleasant all year, as evidenced by the water temperature near Ko Samui.
Summer is very rainy along the west coast, facing the Andaman Sea (see the Similan Islands, Phuket, Krabi, the Phi Phi Islands, Koh Lanta, and Koh Lipe), because the monsoon strikes the coast straight from the sea, whereas there is little rain from December to March.
Furthermore, during the summer monsoon, the sea can be choppy, making it difficult to reach the islands by boat, depending on the day, tours are known to be cancelled during this season if the government issues severe weather and ocean condition warnings.
Mountain ranges with peaks exceeding 2,000 metres can be found in western Thailand, along the border with Burma, and in northern Thailand, along the border with Laos (6,500 feet). The climate above 1,000 metres (3,300 feet) is cool in winter, with mild days and cold nights, and pleasantly warm the remainder of the year. Rainstorms are typically more torrential in mountainous areas, and even before the monsoon, some storms may develop in the afternoons, so this region is typically surrounded by rainforests. Significant rivers including the Mekong and the Salween flow through the basins in between mountains before reaching the plain.
In regards to the cyclones that form in the Pacific Ocean travel from east to west, affecting the mainland part of Thailand after releasing the majority of their energy over Vietnam, Laos, and Cambodia; however, they can still bring torrential downpours. When they take a more southern path, they can have a greater impact on Thailand’s peninsula. They typically strike Thailand from June to December, but are more common from September to November.
Cyclones from the Indian Ocean, on the other hand, follow a track from east to west, or from south to north, and impact the Andaman Sea in the initial phases of their creation, or they can hit the continental part of Thailand after affecting Myanmar more directly. They are less common than typhoons and form more frequently between April and December, with two phases at the beginning and end of the season (April-June and October-December). Although, because of the warm sea, they can develop year round, particularly in the south.
Thailand has not been hit as hard as other Southeast Asian nations such as the Philippines or Vietnam. Peninsular Thailand, in particular, is located in a relatively safe zone from tropical cyclones, and has been directly affected only from mid-October to around December 20 in recent decades (but in 2019 a tropical storm, Pabuk, affected the area in early January). However, a particularly damaging typhoon was Gay, which hit the Gulf of Thailand in early November 1989, and another was Forrest in mid-November 1992.
November would be a pleasant month in many parts of the country if it weren’t for the threat of cyclones.
The Best Time
As previously stated, the best time to visit Thailand is from December to mid-February in the mainland part and in Bangkok, from late December to March on the south-western coast (check out the Similan Islands, Phuket, Krabi, the Phi Phi Islands, Koh Lanta, and Koh Lipe), and from late January to April on the eastern coast of the Gulf of Thailand (see Ko Samui, Pattani, and Songkhla), with the exception of March and April, which are hot months
Mid-summer, in July and August, the weather is usually comfortable enough in the eastern part of peninsular Thailand, that is, the coast facing the Gulf of Thailand, because the area is sheltered from the most intense monsoon rains, which occur on the west side, and generally from tropical cyclones as well.
What to Bring
In the winter, pack light clothes for the day and and a jacket and a hoodie or jumper for the evening in the north (Chiang Mai, Chiang Rai); in Bangkok, light clothing, a light jacket for the evening, a scarf for the cold wind, and possibly a warm coat or sweater for chillier evenings. Pack appropriate clothing for Peninsular Thailand, such as a light jumper for the evening, a scarf for the wind, and a sweatshirt for air-conditioned places. In the Gulf of Thailand, a light raincoat or umbrella is recommended, if you don’t want to travel with too much stuff, you can buy it all when you get there.
When visiting the reef and the islands, usually on all tours, snorkelling equipment is provided (masks and snorkel only) if you wants fins, you should either bring your own or possibly request to pay a little extra on your particular tour to rent some fins for the day. Some suggest to bring rubber soled shoes for snorkelling, this is to protect yourself from walking on anything sharp (please DO NOT walk or stand on and reef or the coral, it is protected and a living organism, and must be left alone)
Bring spring/autumn clothing, a warm jumper, and a pullover for the evening if you are in the mountains.
In the summer, wear tropics-friendly, lighter garments, a light raincoat or umbrella, and comfortable shoes; in air-conditioned places, wear a light sweatshirt and a scarf. Light clothing for the day, a raincoat, hiking shoes, and a sweater for the evening and mountain peaks are recommended in the mountains.
It is necessary to remove shoes, dress neatly, respectfully and conservatively, and cover a little before entering buddhist temples, and other important and cultural sites.