Summer ?
May to September, Bright sunshine and clear skies 
Temperatures - 13.1?C-20.7?C

rainyMonsoon ? ?
June - August, Constant rainfall, fog and occasional landslides 
Annual rainfall - 3894 mm
Winter ? ? ?
November to February, Cold, fog, snowfall is rare 
Temperatures -7.7?C-12.5?C 

      Sikkim is located at the North Eastern part of India and has the best pleasant and alpine climatic condition. It shares its boundary with Nepal, China, West Bengal and Bhutan which makes Sikkim pleasant in term of climate. . 

It has a temperature condition that keeps on varying. The North and West Sikkim is the coolest district, whereas South and some part of East is hot area. 

The intensity of heat is around 36degree C as the highest in the state. In terms of rain it is heavy around May till mid of October. 

July is the wettest month in mostly all the places. The highest annual rainfall for the individual station may exceed 5000 mm. and average number of rainy days (days with gangtok rain of 2.5 mm. or more) ranges from 100 at Thangu in north Sikkim to 184 at Gangtok in east Sikkim.

One can see fog arond the state from May-September. If you move on going the higher altitude (10,000+ ft)their is chilling cold. In the winter od Dec-Jan one can view the beauty of snowfall if the temparature is low.

Summer Time : March to August 

Winter Time : October to february.