Water temperature in Marathon Key (FL) in January
Is it warm enough to swim in Marathon Key in January? Average water temperature in Marathon Key in January is 74.5°F and therefore suitable for comfortable swimming. The warmest sea in Marathon Key in January is 79.9°F, and the coldest is 68.4°F. To find out the sea temperature today and in the coming days, go to Current sea temperature in Marathon Key
Changes water temperature in Marathon Key in January 2025, 2024
To get an accurate forecast for the water temperature in Marathon Key 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 Key, the selected years in the table also show the values of the maximum and minimum temperatures on each of the days of January.
You can choose any other years:
| Day | 2025 | 2024 | Min | Max |
|---|---|---|---|---|
| January 1 | 76.6°F | 72.9°F | 72.1°F | 79.2°F |
| January 2 | 76.1°F | 72°F | 72°F | 79.9°F |
| January 3 | 75.7°F | 72.1°F | 72.1°F | 79.3°F |
| January 4 | 74.8°F | 71.6°F | 71.6°F | 78.4°F |
| January 5 | 74.7°F | 71.4°F | 71.4°F | 77.9°F |
| January 6 | 73.9°F | 72.7°F | 72.7°F | 77.9°F |
| January 7 | 73°F | 73.4°F | 73°F | 78.1°F |
| January 8 | 72.5°F | 73.2°F | 72.5°F | 77.5°F |
| January 9 | 70.9°F | 73.2°F | 70.9°F | 77.2°F |
| January 10 | 68.9°F | 73.2°F | 68.9°F | 76.8°F |
| January 11 | 69.8°F | 72.7°F | 69.8°F | 77.2°F |
| January 12 | 69.3°F | 74.8°F | 69.3°F | 77.2°F |
| January 13 | 69.3°F | 74.5°F | 69.3°F | 76.8°F |
| January 14 | 70.2°F | 74.5°F | 70.2°F | 76.6°F |
| January 15 | 71.1°F | 75.2°F | 71.1°F | 76.6°F |
| Day | 2025 | 2024 | Min | Max |
|---|---|---|---|---|
| January 16 | 71.2°F | 75.9°F | 71.2°F | 76.6°F |
| January 17 | 71.8°F | 75.4°F | 71.2°F | 77.4°F |
| January 18 | 71.6°F | 75.7°F | 71.4°F | 77°F |
| January 19 | 72.9°F | 75.2°F | 71.6°F | 77.2°F |
| January 20 | 72.9°F | 75°F | 71.6°F | 77.4°F |
| January 21 | 72.5°F | 74.8°F | 71.4°F | 76.8°F |
| January 22 | 70.9°F | 74.7°F | 70.9°F | 76.6°F |
| January 23 | 71.1°F | 73.4°F | 69.6°F | 76.8°F |
| January 24 | 69.1°F | 74.5°F | 69.1°F | 76.5°F |
| January 25 | 68.7°F | 74.1°F | 68.7°F | 76.3°F |
| January 26 | 68.4°F | 76.1°F | 68.4°F | 76.3°F |
| January 27 | 69.1°F | 76.6°F | 69.1°F | 76.6°F |
| January 28 | 69.8°F | 77°F | 69.8°F | 77°F |
| January 29 | 70.2°F | 75.9°F | 70°F | 75.9°F |
| January 30 | 71.4°F | 73.9°F | 69.4°F | 76.1°F |
| January 31 | 72.1°F | 73°F | 70.2°F | 76.6°F |
Average water temperature in Marathon Key in January over a decade
| 2016 | 2017 | 2018 | 2019 | 2020 |
| 76.1°F | 75.7°F | 73.8°F | 74.1°F | 75.9°F |
| 2021 | 2022 | 2023 | 2024 | 2025 |
| 73.6°F | 75.4°F | 75°F | 74.1°F | 71.6°F |
Marathon Key sea state in January
Chart comparing the height of waves in Marathon Key in January over the past years. The red line indicates the height of the waves when swimming in the sea is prohibited. To view the current sea conditions, click on the graph.
Marathon Key water temperature during other months:
You can also view information about water temperature for other months by clicking on the month button below
