Hua hin: Annual Weather Averages. April is the hottest month in Hua hin with an average temperature of 30°C (86°F) and the coldest is December at 26°C (78°F) with the most daily sunshine hours at 10 in March. The wettest month is October with an average of 200mm of rain. The best month to swim in the sea is in April when the average sea temperature is 30°C (86°F).