Bhutan's climate is as varied as its altitudes and, like most of Asia, is affected by monsoons. Western Bhutan is particularly affected by monsoons that bring between 60 and 90 percent of the region's rainfall.
Bhutan's generally dry spring starts in early March and lasts until mid-April. Summer weather commences in mid-April with occasional showers and continues through the premonsoon rains of late June. The summer monsoon lasts from late June through late September with heavy rains from the southwest. The monsoon weather, blocked from its northward progress by the Himalayas, brings heavy rains, high humidity, flash floods and landslides, and numerous misty, overcast days. Autumn, from late September or early October to late November, follows the rainy season. It is characterised by bright, sunny days and some early snowfalls at higher elevations. From late November until March, winter sets in, with frost throughout much of the country and snowfall common above elevations of 3,000 metres (9,843 ft). The winter northeast monsoon brings gale-force winds down through high mountain passes.