Haikou's winters are mild, with temperatures rarely dipping below 5°C in January, but still experiencing some chilly mornings. Spring arrives quickly, warming up rapidly to highs around 36°C by March and 38°C by May. The summer months bring warm days, with temperatures often reaching the mid-30s from June to August. Autumn is a slight cool-down, with highs in the mid-to-high 20s by September and October. Winters return, with temperatures dropping back down to around 10°C by December.