Under the influence of seasonally-driven monsoon winds, Thailand enjoys a tropical climate that differs markedly from one region to another. On one hand, the country experiences the southwest monsoon beginning in early May, which brings warm, humid air currents from the Indian Ocean. On the other hand, the northeast monsoon takes hold in August, delivering cold, dry winds from the anticyclone over mainland China. In general, Thailand's climate is characterised by two distinct seasons: a dry season and a rainy season.

The country lies within a tropical zone, just 15 degrees from the equator, which accounts for the thermal stability experienced year-round. The average annual temperature ranges between 19°C and 38°C.

General Characteristics of Two Climatic Seasons

Rainy Season

With the southwest monsoon, the rainy season begins in May and extends through October. The airflow brought by the monsoon triggers significant rainfall across much of the country. Rainfall distribution varies considerably depending on geographical location and topography from one region to another. Precipitation is particularly abundant along the western coast and diminishes as you move north and toward the Korat Plateau in the east.

Dry Season

Driven by the northeast monsoon, the dry season sets in from mid-March through early June. It is shorter in the south due to proximity to the sea, while it lasts longer in the northeast region. Heat can be intense—remember to protect yourself from the sun and stay well hydrated throughout the season. During this period, it's best to head for the coasts to enjoy the sea. You may also venture into the highlands around Chiang Mai where you'll find refreshing cooler evenings.

Regional Climates in Thailand

Northern Thailand

Northern Thailand, particularly Chiang Rai, Mae Hong Son and Chiang Mai, experiences a long, cool dry season due to high mountain ranges. Between December and January, nighttime temperatures can drop to 5°C. In Mae Hong Son, temperatures can even fall to 2°C at night. This part of the country enjoys an intermediate season known as the cool season.

Central Thailand

In central Thailand, including regions like Nakhon Sawan, Sara Buri and Bangkok, the dry season runs from mid-November through mid-February. It brings clear, bright weather with relatively warm temperatures, though mornings and evenings remain cool. Between April and May, the region experiences a hot season with temperatures sometimes climbing to 40°C.

Southern Thailand

The southern regions experience only two climatic seasons, though this can be further divided into the southeast and southwest, which do not experience the rainy season at the same time. The monsoon occurs in the west between June and August, while rainfall reaches the eastern portion from mid-October through mid-December.