The annual monsoon cycles that affect all of mainland Southeast Asia produce a ‘dry and wet monsoon climate’ with three basic seasons for most of Laos. The southwest monsoon arrives in Laos between May and July and lasts into November.
The monsoon is followed by a dry period (from November to May), beginning with lower relative temperatures and cool breezes created by Asia’s northeast monsoon (which bypasses most of Laos), lasting until mid-February. Exceptions to this general pattern include Xieng Khuang, Hua Phan and Phongsali Provinces, which may receive rainfall coming from Vietnam and China during the months of April and May.
Rainfall varies substantially according to latitude and altitude, with the highlands of Vientiane, Bolikhamsai, Khammuan and eastern Champasak Provinces receiving the most.
Temperatures also vary according to altitude. In the humid, low-lying Mekong River valley, temperatures range from 15°C to 38°C, while the mountains of Xieng Khuang it can drop to 0°C at night.
When to go
The best time for visiting most of Laos is between November and February, when it rains the least and is not too hot. It’s also Laos’s main season for both national and regional bun (festivals).
If you plan to focus on the mountainous northern provinces, the hot season (from March to May) and early rainy season (around June) is not bad either, as temperatures are moderate at higher elevations. Southern Laos, on the other hand, is best avoided from March to May, when day-time temperatures break into the 40s and nights aren’t much cooler.
The rainy season is not as bad as you might think. While it will rain – very heavily – the downpours are often fairly brief and can be bracketed by long periods of sunshine. The rains also clear dust from the skies and land, making everything clearer and brighter. Of course, there are downsides; unsealed roads can become quagmires and extensive travel in remote areas like Salavan, Phongsali and Sainyabuli might be impossible. River travel can be a good alternative during these months. If you intend to travel extensively by river, November is the best; flooding has usually subsided yet river levels are still high enough for maximum navigability. Between January and June, low water can make navigating some rivers difficult.
December to February and August are the peak tourist times. January, in particular, is very busy and booking ahead is advisable.