The climate of Chiang Mai is controlled by tropical monsoons and falls into three main seasons. The weather, like in most of Thailand, is typically hot and humid with the temperatures in Chiang Mai are often close to or above to 30°C. From June to late October, you can expect frequent rain and thunder showers.
The weather you can expect when visiting Chiang Mai depends of course on the season. Chiang Mai’s climate can be roughly divided in three seasons, the rainy season, the dry and cool season, and the dry and warm season.