Climatic conditions within Nepal vary from one place to another in accordance with the geographical features. In the north, summers are cool and winters severe, while in the south summers are sub-tropical and winters mild. The monsoon that brings rain from June through September affects most of the country except those that lie in the rain-shadow areas like Mustang which is within Nepal but a part of the Tibetan plateau.
The climate changes rapidly from the sub-tropical terai to the cool dry temperate and alpine conditions in the northern Himalayan ranges within a short span of 200 km. In the terai, which is the hottest part of the country, summer temperatures rise above 45°C. The climate here is hot and humid. In the middle hills, the summer climate is pleasant with temperatures around 25°C – 27°C.
The winter temperatures range from 7°C to 23°C in the terai and sub-zero to 12°C in the mountainous regions, hills and valleys. The northern Himalayan region has an alpine climate with temperatures reaching below -30°C. The valley of Kathmandu has a pleasant climate with an average summer and winter temperatures of 19°C – 27°C and 2°C – 12°C respectively.