As with most areas in Thailand, Chiang Mai varies from hot to hotter for most of the year. It’s a tropical wet and dry climate, but during the dry season the nights can be quite cool compared to the daytime highs. This is one of the many reasons that expats prefer living in the northern part of the country.The nicest time of the year is the dry season which generally lasts from November to April. As the rainy season comes to an end in November, the cloudy days and scattered thundershowers slowly give way to bright sunshine and clear skies for the winter months. Daytime highs still reach into the high 20s C and low 30s C…but you might have to wrap up at night.
Although air conditioning is the norm for most apartments, heating is, for the most part, unheard of. Winter night-time temperatures are much cooler than points further south. Lows can dip below 15 C and sometimes even as low as 4 C. The record low for January is 0 C so be prepared!
As spring arrives, daytime temperatures increase. They’re at their highest in April, when they can squeeze past 37 C on a regular basis. Fortunately, the world-famous Songkran festival also arrives at the beginning of the month. The celebrations are for the Thai New Year and are famous for water pouring rituals…and water fights! Certainly the tradition gives everyone the opportunity to be cooled down by the copious amounts of water being splashed about for several fun-filled days.
Residents look forward to the arrival of the monsoon season sometime in April or May—a relief from the excessive heat and humidity of the past few months. During a normal year, rainfall increases monthly until it reaches a maximum in August or September. But continuous rainfall and perpetual grey days are unusual. More typically, towering storm clouds build during the heat of the day and burst into torrential sporadic downpours late in the afternoon, which can last anywhere from a few minutes to an hour.
Come November, the rainy days begin to diminish and the annual cycle begins again as the climate becomes cooler and drier.