With its more Northern latitude and higher elevation, Chiang Mai enjoys a cooler climate than the stifling central plains near Bangkok. During the hot season, however, the temperature rises quite a bit and the citizens look for ways to beat the heat. Perhaps the rising mercury is the reason why Songkran (the water festival) is celebrated so enthusiastically here. Due to the more tropical location of Chiang Mai, the normal seasons of spring, summer, fall and winter don’t apply. Instead, there are three seasons: Hot, Cool and Rainy.
The cool season lasts from early December to February and is the most popular time to visit Chiang Mai, weather-wise. During the day the temperatures max out at a pleasant 30°C (86°F) but bring a jacket or sweatshirt because the temperature drops rapidly after sunset, sometimes to as low as 10°C (50°F). Riding a motorbike at night wearing a t-shirt may make you wonder whether you’re in Thailand at all and the high mountains can get downright cold. On the upside, rain in the cool season is rare and more than one shower in a month is uncommon.
Chiang Mai begins to warm up after New Year’s and by the middle of March the hot season is in full swing. Daytime temperatures soar to a blistering 40°C (104°F) and it’s not a dry heat, either. The combination of high temperatures and sweltering humidity make exertion difficult and the whole city slows down a bit. The nearby mountains are a great place to escape from the city heat as their high elevation brings mercifully cooler air. Thankfully the hot season is fairly short and the heat wave is over by early June at the latest.
Bringing a welcome relief from the blistering hot season, the rains begin to fall around early June and continue on until late October. The temperature falls to an average of 32°C (89°F) during the day and a pleasant 23°C (73°F) at night. It rains almost every single day during the rainy season but almost never continuously. Typically the day will dawn sunny and bright but the clouds will begin to gather during the afternoon until the downpour starts in late afternoon or early evening. Thai rainstorms are usually intense but short lived. When one starts your best bet is to find your way to a restaurant or pub and relax and wait it out. Typically after an hour or so the rain lets up and the city is washed clean for a clear evening. Another storm during the middle of the night can provide some spectacular lightning shows. The rainy season is a mixed blessing for visitors. One the one hand, the midafternoon showers can become a real inconvenience, on the other the temperature stays cool and the showers bring the local vegetation back to a lush emerald green.