South Australia

The sea in South Australia peaks in February, when the water averages around 21°C.

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

On average, 3 months a year sit above 20°C — the threshold most swimmers describe as pleasant without a wetsuit.

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

Outside peak season the water drops toward 14°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable.

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

South Australia sits in the Southern Hemisphere, so the warmest sea coincides with the December–February summer and the coolest with July–August.

Long-term climatology for South Australia shows an annual mean sea temperature of 17°C, ranging from 14°C in winter to 21°C at the summer peak.

The seasonal swing is roughly 7°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 South Australia, 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.