The first transition occurs around May to Oct in the form of heavy monsoon rains. While Nov to Feb is fairly calm and cool season and Mar to May experiences some of the hottest days in the entire year.
Rainy season is considered to be the worst time to travel, the rains in the region are highly unpredictable and range from slow showers to heavy flooding. The Interior part of the country becomes extremely difficult to travel during the rainy season due to the closure of boating service and bad road conditions.
Thailand has mostly warm and humid climate, but during the cold season this humidity and heat becomes bearable. This period is considered to be the best time to visit as the weather stays pleasant and the roads remain unaffected by any kind of rain or storms.
The cool season also experiences a surge in the travelers coming from around the world and the places can become bit crowded. Another option is to visit the country in the hot season if you don’t have any problem bearing the humid and hot weather of the country.
Thailand has a very diverse topography that is affected differently by the changing weather. The northern part of the country experience most drastic changes in the temperature with changing season while the southern Islands tend to have consistent temperature throughout the year, but the water surrounding this islands gets affected in the rainy season.