Thailand has two distinct climate zones: tropical in the south, and tropical savanna in the north. The temperature varies from 38°C to 19°C with the annual average at about 29°C. The humidity is from 66% to 82.8%.

Weather & Season

The weather in Thailand is always hot and humid, although the northern highlands are generally 5°C cooler. (Note: In the North and Northeast in winter, the temperatures are much lower during night time, especially on the mountains, with temperatures lower than 10°C.) There are three seasons in Northern, Northeastern and Central Thailand - hot (March to May), rainy (June to October), and cool (November to February). And there are two seasons in the South - rainy (April to November) and hot (December to March).

Northern and Central Areas

The northern and central areas of the country (including Bangkok) experience three distinct seasons.

The hot season lasts from March to May, with temperatures averaging in the mid-30°C, with April the hottest month. This period sees very little rain, if any at all.
March - June is especially hot, with average high temperatures in the mid 32-35°C.

The rainy season begins in June and lasts until October; the average temperature is 29°C with 90% humidity. While the rainy season brings frequent showers, it's rare for them to last for a whole day or for days on end. Daily showers will come in torrents, usually in the late afternoon or evening for maybe 3 or 4 hours -- many times bringing floods. Trekking in the north is not recommended during this time.
Avoid the monsoon season mid May - October, when it's particularly humid and rainy (the streets of Bangkok flood easily), though those willing to chance it will get better rates at hotels.

The cool season, from November through February, has temperatures around 26°C, with moderate and infrequent rain showers. In the north during the cool season (which is also the peak season for tourism), day temperatures can be as low as 16°C in Chiang Mai and 5°C in the hills.
The best time to go is November - February, when the days are milder and the nights are cool.

Southern Malay Peninsula

The southern Malay Peninsula has intermittent showers year-round, and daily ones during the rainy season (temperatures average in the lower 30°C.

If you're traveling to Phuket or Ko Samui, it will be helpful to note that the two islands alternate peak seasons somewhat. Optimal weather on Phuket occurs between November and April, when the island welcomes the highest numbers of travelers and the most expensive resort rates.

Alternately, Ko Samui's great weather lasts from about February to October. Refer to each destination's section for more information about peak seasons and weather patterns.

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