What's the temperature in Haikou all year round? Is woolen coat useful?

From the middle and late June of 1 1, the atmosphere turned cold, and then until the middle of March of the following year, the temperature was almost between 14 and 17 degrees. But because Haikou is humid, it is not good to sleep in the cold and quilt at night. Don't say I'm afraid of the cold. I northerners always go home for the New Year at MINUS 15 degrees, so I still have to prepare a coat. This cold feels different.