Advise what to wear during Dec 15 to 19 in Taiwan

There is about 10C of temperature difference between the north and south. And the average temperature of Taipei is about 15℃. But It is humid in this city. In the north of Taipei, thick coat is necessary and if you are afraid of the cold, you'd better the down coat. If you go to the south, a coat is enough except for on the mountainous areas or the seaside.