Nepal has 4 seasons like most countries, starting from Spring (mid Feb to April
Summer (May to August) Fall or Autumn (mid Sept to November) Winter (December to mid Feb) within Summer July and August with monsoon (rainy) season also.
For traveler carry from home light and heavy clothes as per the season of travel in Nepal, as Nepal the land of sub-tropical, mild and cold temperature as per altitude wise in higher elevation in all season above 2,000 meters down jackets and warm clothes are required. From autumn and winter also warm clothes are needed, in spring and summer day time is warm in T-shirts and shorts but in the evening can be cooler.