Thailand's Climate
Thailand's climate is tropical, high both in temperature and humidity, and dominated by monsoons. April and May are the hottest months of the year, when even the locals are moved to complain about the heat. June sees the beginning of the South West Monsoon, and brings with it the rainy season, which continues intermittently until the end of October.
From November to the end of February the climate is much less trying with a cooling North East breeze and a reduction in the humidity level. This is also the main tourist season, and the best time to visit Thailand.
The north and north-east are generally cooler than Bangkok in winter, and hotter in summer. In the far north, around Mae Hong Son temperatures can occasionally drop as low as 2oC.

The climate is very pleasant throughout the year, with temperatures varying from 25 to 34 degrees Celsius.

There are three seasons, warm season from February till May, rainy season from the end of September till November and the "cool" season which extends from October till January.

From February till October, the temperature is of an average of 32 to 38 degrees, but from July till September, there can be some showers, but only for a few hours. 
Rainy season often amounts in fact to some refreshing showers followed by the return of the sun. 

The climate is tropical so very humid all year round, but Samui is always refreshed by a pleasant sea breeze coming from the Gulf.

The island is situated 9.11 N and 99.30 E and at an altitude of about 10 meters above the sea level. 
Best season : from December to June
Rainy season : from the end of September to November