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Seasonal Cycles in Thailand

Climate on the Mainland

The annual seasonal cycle in the more or less “landlocked” provinces of Northern, Northeastern and Central Thailand is divided into the following three seasons:

The “Cool Season” (Thailand’s so-called “winter”) is from mid-October through mid-February:

  • During this period the weather is mostly cool and dry due to the Northeast (Winter) Monsoon. Consequently, these are the best months to visit Thailand, weather-wise. 
  • Due to its being in the tropics, Thailand’s climate is nevertheless quite warm even during this period of the year. Generally, the daily highs are in the low-30°C’s and lows in the mid-20°C’s. However, cold weather fronts brought southwards by the Northeast Monsoon flowing from China occasionally brings the temperature down from the norm by as much as 10C°.
  • The genuinely and consistently “cool” weather can only be experienced in the northern and north-eastern mountains, where the daily highs are in the low-20°C’s and the lows often approach freezing points in the early morning just before sunrise.

The “Hot Season” (our “summer”) is from mid-February through early-June:

  • The temperature gradually climbs starting in the middle of February reaching its peak around end of March and remains VERY HOT through to the middle of May. The average daily highs are in the high-30°C’s and lows in the low-30°C’s. Recently, however, the highs have breached 40°C in many parts of the country, particularly in the Northeaster Region’s lowlands. 
  • During this period, the skies over Northern, North-eastern and Central Thailand are almost totally cloudless, and the sun is directly overhead around noon time. The sun is at right-angle over Bangkok at about noon (12:00PM) on around 26th April every year, which is usually the hottest period for the capital city area. (Note: The sun is in the same position a second time in the year around 16th of August, but there is usually some cloud cover, so the temperature is not as high.)”
  • But it is NOT that bad throughout the period, because when the temperature rises and remains very high for a week or two, gracious and kind Mother Nature often gives relieves in the form of summer showers for a day or two. After that, it’s back o the extreme heat again. Longer lasting relieves come in mid-June with the arrival of the Rainy Season.”

The “Rainy Season” from early-June through mid-October:

  • The Rainy Season is the result of the high humidity Southwest (Summer) Monsoon coming in from the Indian Ocean during this period of the year. As the name suggests, rainfall is heaviest in this season. The average daily highs are in the mid-30°C’s and lows in the low-30°C’s. 
  • Rainfall peaks in August and September, which brings about flood to many low-lying areas and river basins.
  • “When it rains, it pours!” That is exactly how a rain session is in the tropics. A gargantuan mass of rain water falls from the sky is a very short time (say, 20 to 30 minutes). And we seldom get those long dreary days, where it just drizzles non-stop 24×7. Most of the time it is just a heavy downpour for about a half-hour, and that is it. Low lying areas normally suffer short-term flooding, because the huge volume of water simply cannot be handled by the drainage system — and normally, the floods clear within a few hours.

Climate at the Coastal South

The southern coastal regions of Thailand (along the shores of both the Gulf of Thailand and the Andaman Sea) feature only two seasons, i.e. the “hot (and dry)” and “rainy” seasons. Fortunately, Thailand’s two opposite coasts have their respective rainy seasons in slightly different time periods, allowing visitors to find sunny beaches nearly all year round.:

  • On the Andaman coast, the Southwest (Summer) Monsoon brings Indian Ocean’s heavy storms from April to October.
  • On the Gulf of Thailand coast, the most rain falls between November and January (of the following year) due to high humidity from the South China Sea brought on by the Northeast (Winter) Monsoon.
  • While the monsoon on the west coast brings a fairly steady season of continual rain that forces businesses outside the major tourist destinations to shut their doors for the season, the east coast storms are more similar to the north’s, generally sunny days with occasionally heavy downpours.
  • The average temperatures on both sea coasts stay rather constant throughout the year with daily highs are in the low- to mid-30°C’s and lows in the high-20°C’s.