The weather in Chiang Mai is known to be a tropical wet and dry climate. Temperature is controlled by the moderate elevation and the very low latitude of the city, which offers hot weather throughout the year, but the conditions during the night of the dry seasons offer cool temperatures that are significantly lower than the daytime highs.
The best time to travel to Chiang Mai, is anytime really. They do not experience very bad weather conditions often, so besides the weather, you might want to visit the city when it isn’t bustling with tourists, which is usually in November, December and January. You can also travel during the other months but you will need to arrange and organize your stay and everything well in advance.