Monsoon season is approximately from the end of June to the middle of September. About 80% of Nepal's annual rainfall is during that period, so the remainder of the year is pretty dry. Spring and autumn are the most pleasant seasons; winter temperatures drop to freezing, with a high level of snowfall in the mountains, while high summer can be blisteringly hot. Summer and late spring temperatures range from 28ºC (83ºF) in the hill regions to more than 40ºC (104ºF) in the Terai.
In winter, average maximum and minimum temperatures in the Terai range from a brisk 7ºC (45ºF) to a mild 23ºC (74ºF). The central valleys experience a minimum temperature often falling bellow freezing point and a chilly 12ºC (54ºF) maximum. Much colder temperatures prevail at higher elevations. The Kathmandu Valley, at an altitude of 1,310m (4,297ft), has a mild climate, ranging from 19-27ºC (67-81ºF) in summer, and 2-20ºC (36-68ºF) in winter.
Lightweight and tropical clothes with umbrella are advised for June to August. Between October and March, lightweight clothes are worn in Kathmandu, with a coat for evenings and warm clothing for the mountains. When trekking in the mountains, high quality trekking gear that can handle minus temperatures is recommended all year round.