Water temperature in Marathon (ON) in August

Is it warm enough to swim in Marathon in August? Average water temperature in Marathon in August is 15.6°C and therefore is not suitable for comfortable swimming. The warmest water in Marathon in August is 19.4°C, and the coldest is 9.2°C. To find out the sea temperature today and in the coming days, go to Current sea temperature in Marathon

Changes water temperature in Marathon in August 2025, 2024

To get an accurate forecast for the water temperature in Marathon for any chosen month, compare two years within a 10 year range using the chart below. In addition to the sea water temperature in Marathon, the selected years in the table also show the values of the maximum and minimum temperatures on each of the days of August.

Sea temperature

Tides

Weather forecast

You can choose any other years:

Day	2025	2024	Min	Max
1 August	15.7°C	16°C	9.2°C	18.8°C
2 August	15.8°C	17.6°C	9.7°C	18.8°C
3 August	16°C	17.8°C	10.1°C	18.9°C
4 August	15.9°C	18.2°C	10.5°C	18.8°C
5 August	16.2°C	17.7°C	10.8°C	18.3°C
6 August	17.4°C	17.9°C	11.1°C	18.2°C
7 August	17.3°C	17.7°C	11.3°C	18.6°C
8 August	17.9°C	17.8°C	11.5°C	18.7°C
9 August	17.7°C	17.7°C	12.1°C	18.6°C
10 August	17.3°C	17.5°C	12.5°C	18.4°C
11 August	17.9°C	17.3°C	12.6°C	18°C
12 August	17.7°C	16.9°C	12.7°C	18.3°C
13 August	17.6°C	17°C	12.5°C	18.2°C
14 August	18°C	17.5°C	12°C	18.7°C
15 August	17.8°C	17.4°C	11°C	18.8°C

Day	2025	2024	Min	Max
16 August	17.8°C	17.3°C	10.2°C	19.1°C
17 August	17.7°C	17.3°C	10.7°C	19.3°C
18 August	17.8°C	17.4°C	11.7°C	19.4°C
19 August	17.5°C	17°C	11.5°C	19.3°C
20 August	15.4°C	16.6°C	12.4°C	18.9°C
21 August	17.1°C	17.3°C	12.6°C	19.2°C
22 August	16.9°C	17.7°C	13.2°C	18.9°C
23 August	17°C	18.2°C	13.4°C	18.9°C
24 August	17.2°C	18.2°C	13.5°C	18.9°C
25 August	16.3°C	18.4°C	12.9°C	19°C
26 August	15.9°C	18.4°C	13.4°C	18.9°C
27 August	15.8°C	18.4°C	13°C	18.7°C
28 August	13.1°C	18.3°C	13.1°C	18.4°C
29 August	11.2°C	18.3°C	11.2°C	18.4°C
30 August	11.6°C	18.3°C	11.6°C	18.3°C
31 August	12°C	18.1°C	12°C	18.2°C

Average water temperature in Marathon in August over a decade

2016	2017	2018	2019	2020
18.3°C	15.2°C	13.9°C	15°C	16.2°C

2021	2022	2023	2024	2025
17.9°C	14.8°C	14.7°C	17.7°C	16.7°C

Marathon water temperature during other months:

You can also view information about water temperature for other months by clicking on the month button below

Temperature in neighboring cities

The nearest locations with the average water temperature in August. In addition, the maximum and minimum water temperatures for that month, recorded over the last decade, are shown

	Avr	Min	Max
Copper Harbor	16.2°C	7.8°C	20.8°C
Eagle Harbor	16.1°C	6.2°C	22°C
Agawa Bay	18°C	10.2°C	21.3°C
Eagle River	16.4°C	6.1°C	21.3°C
Isle Royale	15.7°C	6.3°C	19.5°C
Grand Marais	17.2°C	7.3°C	21.7°C
Thunder Bay	16.8°C	12.1°C	21.3°C
Calumet	17.9°C	8.9°C	21.9°C
Pictured Rocks	18.2°C	10.5°C	22.4°C
McLain State Park	18°C	9.4°C	21.6°C

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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.

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Date (day and month)

Water temperature: min 16°C

Average temperature Maximum temperature