Month-specific sea-surface temperature · Australia

Port Stephens Sea Temperature in December

20.9°C

69.6°F

In December, sea-surface temperature near Port Stephens has a historical monthly average of 20.9°C. This is not the reading for any particular holiday date.

Across 2023–2025, the lowest and highest yearly December monthly means were 20.2–21.6°C. These are not daily extremes.

Previous month

November · 19.9°C

Change into December: +1.0°C

Next month

January · 22.2°C

Change into next month: +1.3°C

Can you swim or snorkel in Port Stephens in December?

At 20.9°C our temperature-only guide describes the water as cool water. Comfort depends on your cold tolerance, immersion time and wind. A historical average cannot determine whether conditions are safe on any given day.

Do you need a wetsuit?

A 3 mm shorty or full wetsuit will make longer snorkels more comfortable.

Which beach should you choose?

Look for a beach sheltered from the actual forecast waves and wind on your visit. Exposure, currents and entry conditions vary even where water temperatures are similar. Follow local warnings.

Check the current waves, wind and snorkeling forecast →

A live forecast does not predict a future December. Check again close to your trip.

Waves and wind: recorded-model conditions for December

These figures come from a separately modelled, date-specific wind/wave backfill, not the NOAA SST series. A single observed season is not a climatological likelihood or a guarantee of safe conditions.

Compare nearby coasts with their own evidence

Coast	Morning	Afternoon	Period
Jervis Bay	0%	0%	Dec 2025

A “calm hour” meets fixed modelled wave/wind thresholds; neither visibility nor local currents, entry conditions or actual beach safety is measured here. Periods may differ by coast.

Port Stephens Sea Temperature: All 12 Months

Choose a month for available historical evidence, month comparisons and swim guidance. Missing history is clearly marked and never presented as a long-term normal.

January 22.2°C February 22.6°C March 22.4°C April 22.6°C May 21.1°C June 19.9°C July 18.9°C August 18.7°C September 18.9°C October 19.5°C November 19.9°C December 20.9°C

Data source and limitations

Source: Open-Meteo Marine API, MeteoFrance sea-surface temperature; 2023–2025. Marine model grid near -32.72, 152.11. Based on 3 yearly monthly means and 2232 recorded samples. Source methodology.

Modelled sea-surface temperatures do not establish underwater visibility, wildlife, calm currents or safe entry.