Vientiane, the capital of Laos, sits on a bend of the Mekong River on a low plain in the west of the country, facing Thailand across the water at approximately 17.98°N, 102.63°E. It has a tropical savanna climate (Köppen Aw) — hot and humid — with a monsoon-driven wet season and a hot, dry season, and no cool season in the temperate sense.

The hottest months come just before the rains, in March and April, when highs can exceed 34–36°C with rising humidity and hazy skies. The southwest monsoon then brings the wet season from May to October, with heavy afternoon and evening downpours and thunderstorms, peaking in August and September, when the Mekong swells and low-lying districts can flood.

There is no true winter, but the dry season from November to February is the most comfortable time, with warm days around 28–30°C, pleasantly cool nights near 16–18°C, low humidity and virtually no rain. This bright, mild, dry stretch is comfortably the best time of year, before the heat builds again in March.

Vientiane receives on the order of 1,600–1,700 mm of rain a year, overwhelmingly concentrated in the wet season from May to October, with August typically the wettest month, while December to February is nearly rainless. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Vientiane's year is governed by the Mekong: monsoon rains across the vast upstream catchment swell the river dramatically between June and September, and the dry season sees it fall until sandbars emerge. The dry months also bring haze from agricultural burning across the region, which can shroud the city in smoke from February to April.

To follow any single measurement in Vientiane more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.