The most popular time for visiting Chiang Mai ( weather wise) is the cool season, which runs from December to the end of February. It is in fact pleasantly chilly in the evenings, and if you are planning on visiting Chiang Mai at this time of year, it would be wise to bring all-weather gear along; particularly if you intend hiring a motorcycle to get around, or going on a mountain trek. However, don't leave out your summer clothes, as midday temperatures can climb well into the 30s (Celsius).