Weather will likely play an important role when you plan your trip to Gangtok, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually June and August with an average temp of 65°F, while the coldest months are January and December with an average of 48°F. The rainiest months in Gangtok are July, August, June, and September, with each month seeing an average of 36 inches of rainfall.