Nepal has a typical monsoonal two-season year. The dry season start from October and lasts till May and the wet season, the monsoon, from June till September. In the summer (May till early part of June) Kathmandu, the capital city, get very hot with temperatures often in the 30s. Even during winter the bright sunny days often reach 20 digree although with nightfall the mercury may plummet to near freezing. It never actually snows in the Kathmandu Valley and higher up the coldest weather is also the driest weather so snow is unusual. Due to its lower altitude Pokhara is warmer and more pleasant than Kathmandu in the winter, but hotter when the temperature builds up and wetter during the monsoon. The climate of Nepal is of Monsoon type. However, actual climatic condition vary a great deal from South to North of the country i.e., from Terai to the Himalayas . The climate of Nepal has also been influenced by other factors such as latitude, prevailing winds, oceanic distance, and position of mountains. On the basis of seasonal change in climatic conditions, the climate of Nepal can be divided into three main seasons: - Summer, Rainy and Winter Season. The main feature of each season is described below.
Summer Season: The hot weather season begins in March and continues till the end of May. Due to the northward march of the Sun, the high temperature occurs in all parts of the country. During this season, temperature exceeds 30 o C in the Terai. Towards North, altitude increases and it remains warm in midland hills and valleys. It is cool in the Himalayan region. Days become sunny, windy and dusty and it gets hazy in some areas. Most parts of Nepal are dry in this season. However because of great heat, precipitation in the form of rain and sleet occasionally occurs from local convective storms in April and May.
Rainy Season: It begins in June and continues up to the end of September. During this season, monsoon blows from south-east direction and bring rain to the country. The regional distribution of rainfall varies from one to the other area. It depends on the oceanic distance and local topographic features of the place. Pokhara Valley located in the central Nepal receives more than 400 cm rainfall. Similarly, southern slopes of Mahabharat and Churia hills in East Nepal receive more than 200 cm rainfall. In general, rain diminishes from Pokhara Valley towards west and north. In the north, there exists a larger rain shadow area beyond the great Himalayan Ranges in the central and western parts of Nepal . It receives poor rainfall less than 50cm. During rainy season, it gets sultry and humid. Temperature slightly drops down in rainy season due to frequent rainfall.
Winter Season: It includes the month of October, November, December, January and February. During winter season, the sun shines over the southern hemisphere and the temperature becomes very low all over the country. It is about 15 o C temperature in the Terai. The Himalayan zone above 3000m, records the temperature below freezing point. The higher mountain areas are quite cold. On the whole, winter is generally a dry season. The monsoons blow from land to the sea during this season. However westerly wind cause light rain in the western Nepal . Clear sky, foggy or frosty and cold morning are the general features of this season.