i have trip package on dec. but what the local harbin says, they said the best is feb.. so how ?

Hi, actually, you may enjoy yourselves more from late December to early February.
During that time, it may snow a lot so that you will have many things to entertain.
In addition, the Ice & Snow Festival is officially open since Jan. 5th and lasts for one month. I think the local people may want you to enjoy the festival then 'cause it is really fantastic.