Travel time: Year-round
Chiang Mai, located in the mountainous highlands of Northern Thailand, experiences a tropical savanna climate characterized by three distinct seasons: the cool season, the hot season, and the rainy season. Unlike the more uniform tropical weather found in Southern Thailand, Chiang Mai enjoys significant temperature fluctuations, particularly between day and night.
This is widely considered the most pleasant time to visit. During these months, the northeast monsoon brings dry, cool air from China. Daytime temperatures typically hover around 28°C to 30°C (82°F–86°F), while nights can be surprisingly chilly, often dropping to 14°C–16°C (57°F–61°F). In the surrounding mountains, temperatures can even approach freezing.
As the sun moves northward, temperatures rise sharply. April is the hottest month, with daytime highs frequently exceeding 38°C (100°F) and occasionally reaching up to 42°C (108°F). This season is also marked by the "Burning Season" (typically February through mid-April), where agricultural burning and forest fires create a thick haze. The air quality often reaches hazardous levels during this window, and the surrounding mountains may disappear from view behind a wall of smog.
Driven by the southwest monsoon, this season brings much-needed relief from the heat. Rainfall is rarely continuous; instead, it usually arrives in short, intense bursts during the late afternoon or evening. September is historically the wettest month. Between storms, the skies are often bright, and the landscape turns a vibrant, lush green.
In Chiang Mai, the day often starts with a crisp, clear morning, especially in the cool season. High humidity begins to build by midday, particularly from May onward. Locals often plan outdoor activities for the early morning (6:00 AM – 9:00 AM) to avoid the peak solar radiation between 11:00 AM and 3:00 PM, when the UV index is frequently at its highest (11+). By evening, the heat typically dissipates much faster than in Bangkok or the southern islands, thanks to the city's inland location and surrounding topography.
The topography of the Chiang Mai valley creates significant weather variations.
A notable meteorological shift occurs around mid-April during the Songkran (Thai New Year) festival. This period often marks the arrival of the first significant "pre-monsoon" storms. These electrical storms can be violent but are welcomed by locals as they temporarily clear the air of the burning season haze and signal the beginning of the cooling rains.
Locals have a unique vocabulary for the weather. While a Westerner might consider 20°C (68°F) mild, Chiang Mai residents view this as "cold" weather. During the winter months, it is common to see locals wearing heavy puffer jackets and scarves in the morning, which are then shed as the mercury climbs in the afternoon. During the smoky season, life moves indoors into air-purified spaces, while the rainy season is simply accepted as a time of natural renewal, with daily life continuing despite the brief, torrential downpours.