What to wear to Hainan in January

I am now in Hainan. I think the weather is a bit cold recently. Probably need to wear a little thicker. I'm more afraid of the cold, so a pair of thermal underwear + a thicker jacket will do. Just a pair of pants. If wearing a skirt. Be sure to wear tights. But I estimate that after these few days until February, the weather will be a little warmer. Depends on how long you stay. If you are going to carry it for a long time, you can bring a few short-sleeved clothes (in relatively northern areas like Haikou, I guess you won’t need them, but if you go to Sanya, you must wear short-sleeved clothes during the day. Generally speaking, you can still wear them. Long sleeves, but there are many cases where you don't wear a jacket. But this is only when the weather is hot) It doesn't matter if you wear shoes. Better not to have a backpack. Although I have never encountered any thieves in Hainan. But it's hard to say whether you will encounter it. Especially if you are unfamiliar with the place. A crossbody bag would be safer. With the backpack on the back, you won’t even know your money has been stolen. Especially those from out of town. Lost things are troublesome.

ps: Isn’t it almost February now? How do I see that there are 14 days left for your question. Still asking about January 8th.