Yes December is an ideal time to visit Darjeeling and Sikkim. The weather will be cold and snowfall starts by month end. Places to visit in Darjeeling - Nightingale park, rock garden, pagoda, tea plantations, happy valley tea estate, monasteries and museum. Sikkim- Pelling, Ravangla, monasteries, Kanchenjunga park, botanical garden, zoo park. Since it’s going to be winter time, kindly carry all your winter wears.
Darjeeling nd Sikkim are Beautiful Places to be Visited. You can experience Snow during December in Sikkim. In Sikkim You can Visit Gangtok Capital City of Sikkim. Chungthang nd explore North Sikkim's Natural Beauty. In Darjeeling you can Visit Tea Gardens, zoo, Tiger Hill, Mountaineering Institute etc. Happy Journey.
Great time to visit Sikkim & Darjeeling if you love winters. Things to carry:
Warm clothes
woollen socks
muffler
Warm jackets with good
Gloves
Monkey caps Thermals
Comfortable boots
Backpack
Umbrella
First Aid Kit
Camera Happy journey 🙌