Depending on what you are expecting to get out of the visit will determine the best time to visit the area. However, the ideal time to travel here is from the middle of February until May which is when the winter is ending and the summer is just beginning. Also, if you want to get the most breathtaking views from the Khangchendzonga Mountain, then you should visit sometime from the middle of September until the middle of December.
From mid-December until mid–February, the region experiences winter season and this area gets extremely cold and is not the ideal time to visit for sightseeing. Also, from May until September is when the monsoons will arrive and the deluges of rain will spoil your trip.