Nepal has various climates with its scenery. It ranges from hot to cold depending on the elevation. The Terai region, which lies in the tropical southern area of the country, for example, has a hot, humid climate. The mid-land (Mountain Region) is pleasant almost all year around, even though winter morning and nights are cool. The northern (Himalayan) Region, around an altitude above 3,353 meters has an alpine climate with a significantly lower warmth and thin air in winter as can be predictable.
Generally Nepal has flowing four climatic seasons.
(1) Spring: March – May.
(2) Summer: June – August.
(3) Autumn: September – November.
(4) Winter: December – February.
Normally Spring & Autumn are the best season for trekking in Nepal's Mountain however you can do some trekking even the Summer & Winter season but visibility might be poor due to the rain & cloud.
Spring is colorful season which is punctuated by the peculiar shower of life-giving rain but the heat slowly builds until the monsoon break arrives. During summer the Monsoon, moisture -laden wind, meet in the Bay of Bengal and sweep up across India to expend its force on the Himalayan mountain chain. Autumn is well-known for clear sky and pleasant temperature. By winter the high hills acquire dry brown shades and the mountains are infrequently covered with fresh snow. However due to Nepal’s enormous variety of diversified land direction as well it’s incredible climatic difference effects regular seasons different and flowing six in Nepal.
(1) Spring (Basanta) - April-May
(2) Summer (Grishma) - June-July
(3) Monsoon (Barsha) - Late June-Mid September
(4) Autumn (Sharad) - September-November
(5) Winter (Hinud) - December-January
(6) Windy (Sisir) - February-March