The weather in Vientiane is practically the same as the rest of the provinces in Laos, which show tropical climates. There is a slight tendency of higher temperatures and less rainfall than in the northern regions of Laos, however.
Much like the rest of the country, Vientiane experiences three distinct seasons: the cool season, the hot season and the rainy season. Weather is fairly predictable in these diverse seasons except for the occasional discrepancies. Most of the time, seasons are consistent enough for a visitor to be able to easily plan a trip to Vientiane.
The cool season of the city is deemed the best time to visit the city. During late October to March, temperatures are bearably cool and crisp with non-existent rainfall aside from the odd spells during the beginning of the season. The daily highs of the cool season are at around 20 degrees Celsius with the evenings a few degrees cooler. By December, the season brings blue skies and pleasant daytime temperatures that make it the most popular season for tourism. Know though that it rarely feels crowded in the town of Vientiane so there is nothing to worry about when visiting the city during its most pleasant weather conditions.
As the cool season draws to a close, temperatures begin to rapidly increase just in time for the hot season of Vientiane. Commencing in April, the city experiences temperatures at around 35 degrees Celsius at its highs. Humidity is also high at this point with occasional rain showers that make the city even hotter. Travelling to the city during the hot season is possible if you don’t mind sweating through your trip. Dust and haze also hang heavily over the region which often creates rather unpleasant conditions. To help with such soaring high climates, April’s Pii Mai New Year celebration brings water fights to the streets in an effort to help cool locals off. Similar to the famous Songkran Festival in Thailand, the Vientiane version is much more low-key but as exciting and enjoyable. Make sure to get accommodations with air-conditioning as not being able to do so can feel quite hellish, to say the least.
By June, the hot season gives way for the rainy season. Heavy afternoon thunderstorms are normal during this period followed by high levels of humidity. The good thing about the rain is that it generally clears the air of the often dust-choked capital city. Aside from helping the dense vegetation of the city be brought back to life, it also brings with it distinctly cooler atmospheres during the day and most especially at night. The rainy season is not necessarily a bad time to visit, contrary to popular belief, as it does not rain all day long. The rain usually comes in the later afternoon so you have enough time to coordinate your plans for the day.
The weather in Vientiane shares monsoon-driven climates similar to its South East Asian neighbors. However, it is generally a bit cooler than in the hottest countries to the south of the city, making it a pleasant capital to see.