Yes, it will be very cold in Dec and the Jiuzhaigou area will be covered with snow, possibly, it cannot be visited that period. Even if it can be visited, one day is not enough, at least one night stay there.

U need at least 2 days to cover Juizhaigou. Still possible to visit even weather is cold & snowing but it has his natural beauty of 4 seasons throughout the year. Besides Juizhaigou, u can still visit other interesting places. Call me at 86-13808076270 or email me your enquiries I will be happy to assist u.