The climate of Nepal varies enormously as the altitude increases. Each region is divided into a lowland area and an area of very high altitude, so you always need to be prepared if you are planning to go into the mountains. In general, the best time to traevl to Népal is from October to May, during the dry season. Temperatures are high, especially at Katmandu, but it doesn't rain, unlike during the months of June, July, August and September. If you are going on a trek, avoid the months of December and January, which are very cold, especially at high altitude. Avoid visiting Katmandu in May and June, when the heat is unbearable and there is a great deal of mud. So go to see the highest peaks in the world, or to discover the Buddhist and Hindu temples, in the dry season.