Thailand’s climate is subtropical throughout most of the country, leading to year-round hot and humid conditions.
During the hottest months of the year, temperatures regularly top 40° C (105° F). Even during the cooler “winter” season you can expect daily highs to be around 30° C (86° F).
Things do cool off occasionally. Temperatures in the north can sometimes reach 10° C (50° F) at night, so bringing a few long-sleeve shirts for these cool days is advised. It is only in the high mountains that you will find temperatures dropping to freezing or below.
Although the temperature and humidity varies slightly across the different seasons, it is the amount of rainfall that really defines the seasons in Thailand.