The average temperature in Kiawah Island in December for a typical day ranges from a high of 63°F (17°C) to a low of 52°F (11°C). Some would describe it as moderately chilly with a gentle breeze. For comparison, the hottest month in Kiawah Island, July, has days with highs of 87°F (30°C) and lows of 79°F (26°C).