Weather - Northern Thailand
Lanna's weather has the same three seasons as most of Thailand. But the seasons for Northern Thailand vary just a bit and, depending on how far north, cool can equal cold.
Thailand's Weather Seasons
Thailand's Cool Season
is generally considered November to February. The really cool months are December and January.
Elevation has a very strong influence on the temperature. Cold snaps in the mountainous areas of Chiang Mai, Chiang Rai and Phrae can send temperatures to near zero. Very occasionally, snowfall is recorded on top of Doi Inthanon.
You may be more comfortable with long sleeves at early morning and evening. If you plan on hiring a motorcycle, take or plan on buying a warm jacket.
This is also the best time of year for trekking.
Thailand's Hot Season
Lasts from March to May / June, following on the heels of the cool weather. Very little rainfall occurs in the cool season. Oddly, there always seems to be a rainstorm .. and sometimes a hail storm .. during Songkhran in Chiang Rai.
While Lanna is generally considered the temperate region of Thailand, the month of May can be a scorcher with temperatures in the low 40's C.
If you plan on trekking, moderate your activities and drink copious amounts of water.
Thailand's Rainy Season
During the monsoons, usually from June thru October, Thailand starts turning green. Streams and river swell and overflow with some excellent white water rafting.
During the rainy season you may not see rain for a week at a time. Much of the rainfall will be at night with sparkling clear days. The skies may open for an hour or so then give way to a clear day.
Expect two to three days of rainfall per week.
While white water rafting is great during the rainy season, trekking is less fun because of slippery trails.