Water temperature in Marathon (ON)

This data the coastal Marathon 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 water temperature in Marathon

Water temperature in Marathon today is 12.6°C. Based on our historical data over a period of ten years, the warmest water in this day in the Lake Superior near Marathon was recorded in 2024 and was 16.8°C, and the coldest was recorded in 2014 at 11°C. Water temperature in Marathon is expected to rise to 13.1°C in the next 10 days. September average water temperature in Marathon is 15.1°C, the minimum temperature is 9.3°C, and the maximum is 18.3°C.

Throughout the year, the water temperature in Marathon does not rise above 20°C and therefore is not suitable for comfortable swimming. The average water temperature in Marathon in winter reaches 2.8°C, in spring 1.5°C, in summer the average temperature rises to 10.2°C, and in autumn it is 11.2°C.

Marathon water temperature now

Surf Forecast in Marathon 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 Marathon. 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 Marathon. Data in table shown for 26 September 2025, time in GMT 0 format (you can change the time zone on the sea state forecast page)

Surf report in Marathon

Marathon weather forecast

Current temperature and weather

Data in a table show Marathon temperature today (26 September 2025). For more information and forecast for a few days, go to the weather forecast Marathon.

0-3 h	3-6 h	6-9 h	9-12 h
10.9°C	9°C	8°C	9.8°C

12-15 h	15-18 h	18-21 h	21-24 h
15.3°C	17.1°C	15.6°C	11°C

Marathon water temperature by month

These figures shows the average, minimum and maximum monthly water temperature in Marathon. 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 Marathon 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 Marathon

The nearest beaches and cities from Marathon 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
Copper Harbor	14.8°C	11°C		0.48 m
Eagle Harbor	15.8°C	11°C		0.42 m
Agawa Bay	15.7°C	14°C		0.27 m
Eagle River	16.2°C	17°C		0.42 m
Isle Royale	14.6°C	16°C		0.29 m
Grand Marais	15.3°C	17°C		0.62 m
Thunder Bay	15.3°C	19°C		0.16 m
Calumet	15.9°C	18°C		0.47 m
Pictured Rocks	15.5°C	17°C		0.61 m
McLain State Park	16.1°C	19°C		0.48 m

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Our report for Marathon 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.