The climate in Chiang Mai is comprised of three seasons.
A "Cool Season" from the end of October to the end of February during which it is warm during the day and not hot, and cool at night and almost chilly for foreigners and cold for Thai's.
Sunny skies virtually every day from November to end of February will almost no rain. Ideal temperatures to visit Chiang Mai and considered High Season and virtually all accommodations providers increase their rental rates during this period of time.
From March to May we experience our "Hot Season" where we witness a marked increase in temperatures and from June to late October we have our "Rainy Season" where some days we experience a sudden afternoon shower which ends as quickly as it started and dries as quickly, and the ocassional days where it rains through most of the day and night. Monsoons come in from India and some people don't mind the rain as it does cool things down while other people learn to tolerate it and adjust their schedules accordingly.
During the rainy season "Songkran" the Water Festival is celebrated in Chiang Mai and although it may appear childish when I sees adults throwing pails of water at each other it does offer an opportunity to get soaked, to cool down, to laugh with Thai and foreigners who visit Chiang Mai for the festival.
Chiang Mai is located about 450 miles north of Bangkok and with it's higher elevation Chiang Mai is the beneficiary of a cooler climate compared to Bangkok and southern cities such as Pattaya and Phuket. A definite temperature advantage for retiree's who like warm weather but find hot weather difficult to accept. And this is one of the reasons retiree's have selected Chiang Mai as their retirement home and made Chiang Mai the most popular retirement destination in all of Thailand and in S.E. Asia.
During the cool season temperatures run from a minimum of about 10°C (50°F) to a maximum of about 30°C (86°F). You may need a light jacket or sweater in the evenings and especially if you plan on a tour to Doi Inthanon National Park or higher altitude nearby sites such as Doi Suthep or Chiang Dao.
For about 8-9 months of the year one will require a blanket when sleeping at night. We find that some people are surprised by this but we have lived here long time to attest to this fact. The temperatures are almost ideal for retiree's for most of the year. The cooler climate also reduces the cost of living here as one need not spend as much here as compared to Bangkok, Pattaya, or Phuket for power (air con).
