Weather in Hilton Head Island in March. The average maximum daytime temperature in Hilton Head Island in March is a comfortable 20°C (68°F). There are usually 8 hours of bright sunshine each day, which represents 63% of the 12 hours of daylight. The average sea temperature in and around Hilton Head Island in March is 16°C (61°F). Expect 104mm (4.1 inches) of rainfall across the whole of March with 9 days with some rain falling. Maximum UV levels will be high (7 UV index) at midday when the skies are clear.