Best time to visit Sikkim: There are 3 seasons for visiting Sikkim.

Summer : Summer is from mid-April till the end of May after which the monsoons break at the beginning of June. This is the time when the rhododendrons are in full bloom in places like Yumthang, Varshey (West Sikkim-2 day trek) etc. The skies are fairly clear with occasional showers. This is one of the best times to go on treks.

Autumn : This is a great season when the skies are clear and the mountains are preparing for the winter months ahead. The snow clad peaks should now be visible with the air at its cleanest after 4 months of torrential rains.

Winters : This is the season for those who dare. A visit to Yumthang Valley in winters offers an awesome panorama of a wilderness under a sheet of snow. Tsongo Lake is frozen solid and remains that way till Feb-March. Even in early April one can frolic in the ice in Yumthang and Tsongo, although it doesn't normally snow there in April. But be warned, it's really cold out there!