Chiang Mai enjoys a cooler climate than other areas in Thailand and a holiday here can be enjoyed all year round. While it does experience a hot season, this is still somewhat milder than in Bangkok and certainly less humid. Like elsewhere in Thailand, the north sees three distinct seasons: the hot season, the rainy season and the cool season.
The hot season lasts from March until June and sees daily temperatures ranging between 30 and 35°C. The city becomes very dry and dusty and the air can become hazy with smoke from crop burning (for harvesting purposes). It is the least recommended time of year to visit, although you are guaranteed less crowds and therefore cheaper prices. There are also occasional thunder storms during this period, although they can actually be a welcomed relief.
Rainy season arrives in July and lasts until the end of September. The countryside once again becomes lush and trees and flowers bloom. Despite its name, it does not rain every day and often showers are short and refreshing. There can of course be longer spells of rain which cool things right down. If you decide to visit during this time, don’t forget to pack an umbrella and some waterproofs if you are going trekking. Flooding can be a problem in the city as the Ping River reaches bursting point, but bad floods are rare and mild flooding is usually cleared up quickly.
If you’re not keen on rain and don’t particularly want to roast in the basking sun of the hot season, the cool season (October to February) is the time to come. This is Chiang Mai’s peak season and the city welcomes not only a rush of overseas tourists, but also many Thai tourists escaping Bangkok. There is little or no rain during this period and blue skies are guaranteed. It is the perfect climate for sightseeing, sunbathing or trekking with temperatures dropping to the mid 20's°C. Evenings can get a little chilly, so a light jacket or jumper is recommended.