Laos weather, like the country, varies wildly from chilly to sultry heat, from localised drought to monsoon flooding.
It is a tropical monsoon climate and the entire country lies within the tropics; though the high north and east can feel semi-tropical with dipping temperatures and entrancing mists among the peaks and forests.
The whole country, stretching south-east from Burma and China to the sauna of the south between Vietnam, Cambodia and Thailand, is affected by Asias monsoon cycles that produce three main seasons: the rainy season that can begin at any time between May and July as the southern monsoon blows and end in November; the cool dry season from then until March, the effect of the north monsoon which does not blow over Laos but bathes it in cool winds; and the hot dry season from around March to the start of the monsoons.
Generalisations mask the localised differences but some phenomena seems to be predictable: the Bolaven plateau in the south gets the most rain with 3,700mm a year in places and the amounts decline towards the north-west with Vientiane getting about half that amount and Luang Prabang getting about a third.
The Boleven plateau is a good example of how the weather can vary markedly in quite close areas: Khong in the Champassak district gets around 1,600mm of precipitation annually, compared with Paksong, also in Champasak district, which benefits from between 2,500 and 3,700mm. The surprisingly delineated rainfall variations in Laos can be seen in detail on a map published by the official Visit Laos site (see our links panel on this page).
Between 75% and 90% of rain falls during the monsoon season. But the wettest periods vary with the location: in Vientiane, most rain falls from May to September but in Luang Prabang, August is by far the wettest month.
Air humidity is around 70-85%.
Temperatures, unsurprisingly, depend on altitude and latitude the high peaks in the north and in the Annamite mountains bordering Vietnam in the east are far cooler than the lowlands along the Mekong.
The lowest temperatures are generally reckoned to be about 13C (56F) and the highest can creep into the high 30s (around 100F), though the lowland areas tend to be hot all year and the mountains can be cool at night even in warmer months.
The Mekong, placid in the dry season but full of nature's power during the monsoons