Because of its elevation, Nepal can be divided into three zones – the high mountains, the mid-hills and the flat plains called the Terai. The Everest, Langtang and Annpurna trekking destinations in the mountains are cool throughout the year. The mid-hills, including Kathmandu and Pokhara, are cool except in the summer months from May to July. Temperatures in these cities during the summer remain much cooler than in many cities of the region. Lumbini, Chitwan and Janakpur in the Terai plains are hot in summer (March –July) but cold in winter (December-February). So if you are going trekking, the best months for walking are between September and November and between February and May when the weather is fair during the day and the temperatures do not drop rapidly during the night.
[Source : Ministry of Culture, Tourism and Civil Aviation]
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