Thailand has three main seasons:
Thailand weather is largely determined by the Northeast and Southwest monsoons.
Weather in the South of Thailand
The weather in the South of Thailand is defined largely by the Southwest monsoons. Temperatures rarely drop low enough to result in a cold season and the seasons are largely divided into rainy season and hot season. Southern Thailand has the highest rainfall with around 2,400 millimetres every year which compares with the central and northern regions of Thailand which get around 1,400 millimetres per year.
The rain comes at different times of the year on the West and East coasts as the Southwest monsoon brings rain and sometimes heavy storms to the West coast from April through to October, whilst on the east coast most of the rain falls between September and December. Khao Sok, situated between these two coasts and at a slightly higher altitude is sheleterd from the worst of the stormy weather.
Weather in the North of Thailand
The effects of the Northwest monsoons result in heavy rainfall in the North from June through to November. After the monsoons move away the higher altitudes found in the North of Thailand mean that these foothills of the Himalayas enjoy some much cooler weather especially between the months of November to February. This cooler air also results in a dry season with minimal rainfall. However from april through to June the temperatures and humididty build staedily until the rains finally arrive. It is no coincidence that the arrival of rain is closely associated with the famous Songkran water festival.
Generally whether it is raining or dry the Thailand weather temperatures remain pleasantly mild making a visit to Thailand a rewarding experience all year round. These mild temperatures and abundant moisture result in a fabulously rich environnment in which flora and fauna enjoy a vibrant exisitance.
This information from the Thai Meteorological Department gives details of present conditions and is a rich source of up to the minute detailed reports of Thailand weather.