Hey!
The best season for visiting Yumthang Valley, Lachung and Zero Point Sikkim starts in late February and continues up to mid-June. That’s the time when thousands of colorful flowers are found blooming, spreading fresh vibes and you can witness the real natural beauty of the place. Rhododendrons also in their full bloom and you would witness beautiful views of the mountain ranges, September – December months would be ideal.
However do check routes and other covide protocols before visitng.
Happy traveling :)