Thailand predominantly has a tropical wet and dry or savannah climate while the south and the eastern tip of the east have a tropical monsoon climate.[31]
Most of Thailand has three seasons:
The cool dry season from late-November–February. Temperatures in December for Chiang Mai average around 15 Celsius at night, rising to around 28 Celsius during the day with clear sunny skies. Higher up in the mountains, temperatures may drop to near freezing at night. In Bangkok and in the central and northeastern plains of Thailand, midday temperatures during the cool dry season average around 30 Celsius and the humidity is much lower.
The hot dry season from March–May can see daytime temperatures in the mid- to high-30s. This is the time for holding festivals (such as Songkran and Rocket Festival) to mark the coming of the rainy season.
The rainy season from May–October has daytime temperatures in the low-30s with nighttime temperatures in the mid= to high-20s. Some areas have a relatively short rainy season, such as Ko Samui where it is typically only approximately 6 weeks, starting in October and running through November.[32] Rain showers mainly occur late-afternoon or early-evening. Typically, humidity is high.
Deeper south on the Kra Isthmus with its tropical monsoon climate, daytime temperatures year-round tend to hover around 31 Celsius with only a marked increase in rainfall during the monsoons. The west coast is affected by monsoons from May–October, the southeast coast of the isthmus is affected from October–January.