Shelly Beach Manly Water Temperature & Swim Forecast

The sea in Shelly Beach Manly peaks in February, when the water averages around 23°C.

The main swimming season runs from November – April, 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 October and May are noticeably cooler but often quieter, with fewer crowds and steadier weather.

Outside peak season the water drops toward 16°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable.

The coldest month is typically July at around 16°C, when cold-water swimmers dominate the coast.

Shelly Beach Manly 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 Shelly Beach Manly shows an annual mean sea temperature of 19°C, ranging from 16°C in winter to 23°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 Shelly Beach Manly, 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.