Sikkim is in the grip of severe cold wave.Heavy snowfall has been reported in the higher reaches of the state. These include Nathu la and Chhangu in East district and Lachen, Lachung and Dzongu in North district.The weather remained cloudy for the last two days combined with intermittent drizzle, forcing most of the residents indoors, in the capital Gangtok and in other parts of the state.