Thailand’s climate varies greatly depending on the region. The graph below gives an indication of average temperatures and rainfall in the southern area.

Thailand´s monsoons arrive around July and last into November (the ´rainy season´). This is followed by a dry, cooler period from November to mid-February, followed by much higher relative temperatures from March to June.

There is no real bad time to go, especially in the south, but generally speaking December to May would be considered the best time. 

                         Jan      Feb      Mar     Apr     May      Jun

Temp (°C)         26       27        28         29        29          28

Rainfall (mm)   130     70        75          80       145        110                        

                        Jul       Aug      Sep      Oct      Nov       Dec

Temp (°C)        28       28         27         27       26           26

Rainfall (mm)  115     112       112       300     490         210