Why is Vladivostock so cold, while Dalian is so warm?
Vladivostok (this is the spelling I've always seen) is located at 43º08'  N whereas Dalian lies at 38º05' N.   Five degrees make a difference.  Also, Vladivostok gets more influence from the cold Oyashio current than does Dalian.  For these reasons summers are warmer in Dalian and winters are colder in Vladivostok.