Autumn, from September to November, is cool with clear skies, and is the most popular trekking season. In winter from December to February, it is cold at night and can be foggy in the early morning but afternoons are usually clear and pleasant, though there is occasional snow in the mountains. Weather condition in Nepal vary from region to region. Summer and late spring temperatures range from more than 40 Degrees Celsius in the Terai to about 28 Degrees Celsius in the hilly region of the country. In winter, average maximum and minimum temperatures in the Terai range from a mild 23 Degrees Celsius to a brisk 7 Degrees Celsius while the central valleys experience a chilly 12 Degrees Celsius maximum temperature and a minimum temperature often falling below freezing point.
Much colder temperatures prevail at higher elevations.
The Katmandu Valley situated at an altitude of 1310m, has a seasonable but equable climate with average summer and winter temperatures of 27 Degrees Celsius to 19 Degrees Celsius and 20 Degrees Celsius to 2 Degrees Celsius respectively. The annual rainfall in Katmandu generally exceeds 1300mm. The mean annual precipitation ranges from more than 6000mm along the southern slopes of the Annapurna range in central Nepal to less than the 250mm in the north central portion near the Tibetan plateau. Amounts varying between 1500 and 2500mm predominate over most of the country.