Nepal is a place of having diversified climate. In each nook and corner of every footstep, you may experience preferable weather condition. So, you can easily cope with as per your choice able clothes.
But, Nepal is one of the culturally rich and morally extended, historic countries. So, you are free to wear clothes as per your need.
You can wear T-shirts, fleece, windbreaker, shorts, lightweight pants, sports pants, shirt/pants etc.