Western Australia

The sea in Western Australia peaks in February, when the water averages around 23°C.

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

On average, 8 months a year sit above 20°C — the threshold most swimmers describe as pleasant without a wetsuit.

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

The coldest month is typically July at around 18°C, when cold-water swimmers dominate the coast.

Western 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 Western Australia shows an annual mean sea temperature of 20°C, ranging from 18°C in winter to 23°C at the summer peak.

The seasonal swing is roughly 5°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 Western 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.