Portsea Beach Water Temperature & Swim Forecast

The sea in Portsea Beach peaks in January, when the water averages around 19°C.

On average, 0 months a year sit above 20°C — the threshold most swimmers describe as pleasant without a wetsuit.

Outside peak season the water drops toward 12°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable.

The coldest month is typically July at around 12°C, when cold-water swimmers dominate the coast.

Portsea Beach 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 Portsea Beach shows an annual mean sea temperature of 16°C, ranging from 12°C in winter to 19°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 Portsea Beach, 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.