Hilton Head Water Temperature & Swim Forecast

The sea in Hilton Head peaks in July, when the water averages around 29°C.

The main swimming season runs from May – October, when surface temperatures stay comfortable for extended sessions.

On average, 6 months a year sit above 20°C — the threshold most swimmers describe as pleasant without a wetsuit.

Shoulder months like April and November are noticeably cooler but often quieter, with fewer crowds and steadier weather.

Outside peak season the water drops toward 18°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable.

The coldest month is typically January at around 14°C, when cold-water swimmers dominate the coast.

Long-term climatology for Hilton Head shows an annual mean sea temperature of 21°C, ranging from 14°C in winter to 29°C at the summer peak.

The seasonal swing is roughly 15°C between the coldest and warmest month — a useful yardstick when comparing years or checking whether the current sea is running above or below average.

Recent decades have trended slightly warmer at Hilton Head, in line with regional sea-surface temperature records for the wider basin.

Monthly averages below are drawn from multi-decadal climatology and are updated as new observations arrive.