Thailand’s climate is subtropical throughout most of the country, leading the weather in Thailand 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 vary slightly across the different seasons, it is the amount of rainfall that really defines the seasons in Thailand.
The Best Time to Visit Thailand:
Generally speaking, the best time to visit Thailand is from November to February when most parts (except the south) of Thailand experience the cool and dry season, with temperatures ranging from 29°C to 33°C (84°F to 91°F). The gorgeous weather conditions make these months the busiest time in Thailand.
March to June is generally very hot, and temperatures can reach up to 40°C (104°F) in Bangkok. From May to October is the rainy season in Thailand (from Bangkok north). If you ask the worst months to visit Thailand weatherwise, in Bangkok that would be April, which is the hottest month, and September, which is the wettest month.
The Cool and Dry Season — November to February:
The cool and dry season in central and northern Thailand is from November to February when average temperatures across the region vary between 19°C and 28°C (67–82°F). There are large temperature differences across Thailand in this season, with cities in northern Thailand’s mountains such as Chiang Mai and Chiang Rai reaching record lows of 4°C (39°F), though their average lows are around 15°C (59°F). Therefore, if you visit Thailand during this season, remember to bring some warm clothes.
Bear in mind that, the dry and cool season is the best time to visit most parts of Thailand, except the eastern coast of the Gulf of Thailand, such as Ko Samui, which experiences its torrential rainy season from September to December.
The Hot Season — March to June
Thailand experiences hot weather between March and June. April is the hottest month when temperatures can easily push into the high 30s Celsius (the upper 90s Fahrenheit) and even past 38°C (100°F) in some central cities like Bangkok. The exception to the rule is the southern islands like Koh Samui, where sea breezes keep moderately hot afternoon temperatures to around 32°C (90°F).
The Rainy (Monsoon) Season — May to October
In central and northern Thailand and the southwest coast (Phuket, Krabi…), the rainy season is from May to October, with September and October experiencing the highest rainfall. Rainfall typically occurs as a heavy but predictable afternoon downpour that rarely is cause for canceling travel plans for the day. Average temperatures in Thailand are 25–30°C (between the mid-70s and mid-80s Fahrenheit).
