Auckland

The sea in Auckland peaks in January, when the water averages around 18°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.

Auckland 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 Auckland shows an annual mean sea temperature of 15°C, ranging from 12°C in winter to 18°C at the summer peak.

The seasonal swing is roughly 6°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 Auckland, 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.