Is it better to spend 5 days in Haikou or Sanya in the end of May?

Hi, Matteo. Comparatively speaking, it will rain a lot in that week, while the most days in Sanya will be cloudy. Therefore, I advise you to spend a vacation in Sanya. According to the history data, the temperature in Haikou will range from 75F to 95F and it will have the thunder shower in most days at that time. It will be 80F to 90F in Sanya. It will be cloudy and sometimes rainy. As a result, Sanya could be a better choice for you to swim and play with families.