Though Thailand is warm throughout the year, the climate does vary. Make sure you choose the right time to get the most from your visit.
Central Thailand, the north, northeast and east have three seasons: hot (February / March to June), rainy (June to September / October) and cool (October to January / February). Countrywide, humidity is high almost all year.
Temperatures in Bangkok are mostly hot, with highs of around 35 C [95 F] in April, dropping to roughly 30 C [86 F] in December. This is the best time to visit, when cool breezes make sightseeing much more pleasant. The monsoon rains usually come in brief
but heavy downpours - sometimes producing flash floods - followed by sunshine.
The north (especially Chiang Mai, Chiang Rai and Mae Hong Son) and the northeast can become chilly around New Year, with night-time lows of 11-13 C [52-56 F]. Bring warm clothing. However, daytime temperatures are in the high 20s [70-80
F], reaching the mid-to-high 30s [95-105 F] in April. Rainfall, although not as heavy as in Bangkok, may make trekking a challenge from July through September, but this is when the north is at its greenest. October to January is probably the most comfortable
period for trekking.
The south, roughly from Prachuap Khiri Khan to the Malaysian border, has two seasons; rainy and dry. It is always hot and humid, and the rainfall here is heavier than the rest of the country, especially from March through November. Temperature
highs range from 30-36 C [85-96 F] on the eastern side of the southern peninsular and dip slightly on the western side, from 28/29 C to 33/34 C [80 F to 90 F]