Water temperature in Stewart Island

This data the coastal Stewart Island sea water temperature today, tomorrow and the upcoming days. Besides, you can also get information about the weather and surf forecast, as well as the data on sunrise / sunset and moonrise / moonset at a given point on any given day.

Current sea temperature in Stewart Island

Water temperature in Stewart Island today is 11.8°C. Based on our historical data over a period of ten years, the warmest water in this day in the Tasman Sea near Stewart Island was recorded in 2017 and was 11.9°C, and the coldest was recorded in 2007 at 10.6°C. Sea water temperature in Stewart Island is expected to drop to 11.5°C in the next 10 days. September average water temperature in Stewart Island is 11.4°C, the minimum temperature is 10°C, and the maximum is 12.6°C.

Throughout the year, the water temperature in Stewart Island does not rise above 20°C and therefore is not suitable for comfortable swimming. The average water temperature in Stewart Island in winter reaches 11.7°C, in spring 11.8°C, in summer the average temperature rises to 14.3°C, and in autumn it is 14°C.

Stewart Island water temperature now

The sea salinity in Stewart Island is 34.63‰, and the average salinity of the World Ocean is 35‰.

Surf Forecast in Stewart Island for today

Another important indicators for a comfortable holiday on the beach are the presence and height of the waves, as well as the speed and direction of the wind. Please find below data on the swell size for Stewart Island. We calculate the swell size based on the mean wave height (trough to crest) of each third highest wave. For more information on surf forecasts for the next ten days, please visit sea state forecast Stewart Island. Data in table shown for 21 September 2025, time in GMT 0 format (you can change the time zone on the sea state forecast page)

Surf report in Stewart Island

Stewart Island weather forecast

Current temperature and weather

Data in a table show Stewart Island temperature today (21 September 2025). For more information and forecast for a few days, go to the weather forecast Stewart Island.

0-3 h	3-6 h	6-9 h	9-12 h
5.5°C	4.9°C	4.5°C	8.4°C

12-15 h	15-18 h	18-21 h	21-24 h
11.5°C	12.3°C	10.6°C	9.5°C

Stewart Island water temperature by month

These figures shows the average, minimum and maximum monthly sea temperature in Stewart Island. In addition to the table values, the graph below displays of changes average surface temperature during the year. Values are calculated based on the data over the past 10 years. Using them, you can check the water temperature in Stewart Island on any day of this period that interests you. Click on the month link and you will see a table for each day, or alternatively you can view the temperature curve of the month and select 2 different years you want to compare, either in a table or as a curve

Chart monthly average water temperature in Stewart Island

The nearest beaches and cities from Stewart Island with the water temperature today, as well as the air temperature and the state of the weather during the day and the average wave height for today

	Water	Weather		Wave
Bluff	10.8°C	13°C		1.54 m
Tomahawk Beach	10.3°C	13°C		0.94 m
Port Chalmers	10.1°C	11°C		0.78 m
Big Bay	12.7°C	1°C		3.31 m
Oamaru	10.1°C	13°C		1.55 m
Jackson Bay	12.4°C	10°C		3.75 m
Timaru	10.3°C	14°C		1.35 m
Hokitika	12.3°C	10°C		3.06 m
Christchurch	10.9°C	15°C		1.13 m
Corsair Bay	10.9°C	15°C		1.13 m

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Our report for Stewart Island is compiled using satellite data together with in-situ observations to get the most reliable daily data of sea surface temperatures, surf forecasts, current temperatures and weather forecasts.