Marathon — Water Temperature, Sea Conditions & Trends
This page provides clear and up-to-date information about water temperature for Marathon (Florida, United States). It includes the current water temperature, daily data for the last month presented in a simple chart, and a 7-day forecast. The page also compares today’s value with typical averages for this period, shows usual monthly ranges during the year, and lists nearby beaches with short descriptions. Local weather for the next few days and general details about Marathon help you plan your visit and choose the best time for swimming.
Current Water Temperature
Water temperature in Marathon in the Gulf of America today is 27°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature ranges from 79°F (26°C) to 82°F (28°C). This is very warm water, allowing for extended stays without any discomfort. Swimming in these conditions will be particularly enjoyable, making it the ideal temperature range for those who want to relax in the sea. Additionally, water in this temperature range is suitable for children and elderly people, as it is comfortable for prolonged stays.
It is important to note that these swimming tips and recommendations apply only in good weather. When the air temperature is below 68°F (20°C), and sometimes even below 77°F (25°C), swimming can be unpleasant even with relatively high water temperatures.
Water Temperature Chart Over the Last 30 Days
Water temperature in Marathon has fallen over the last month but risen over the last 7 days. Currently, the sea water temperature at this location matches the average for this day in previous years.
According to our forecast, Water temperature in Marathon will be 26.1°C in the next 7 days. See the table below for daily data for the upcoming week.
Table of Daily Sea Temperature Data
| Date | Current | Average | Forecast |
|---|---|---|---|
| OCT 26 | 27.8°C | 27.5°C | |
| OCT 27 | 27.7°C | 27.8°C | |
| OCT 28 | 27.2°C | 27.5°C | |
| OCT 29 | 26.8°C | 27.5°C | |
| OCT 30 | 26.8°C | 27.8°C | |
| OCT 31 | 26.9°C | 27.8°C | |
| NOV 1 | 26.9°C | 26.3°C | |
| NOV 2 | 27.2°C | 27.0°C | |
| NOV 3 | 27.3°C | 26.5°C | 27.3°C |
| NOV 4 | 26.5°C | 27.1°C | |
| NOV 5 | 25.5°C | 27.0°C | |
| NOV 6 | 25.5°C | 26.8°C | |
| NOV 7 | 25.5°C | 26.6°C | |
| NOV 8 | 25.5°C | 26.5°C | |
| NOV 9 | 25.5°C | 26.3°C | |
| NOV 10 | 25.8°C | 26.1°C |
* Current - Actual water temperature value
** Average - Average water temperature on this day in recent years
*** Forecast - Our water temperature forecast
Actual nearshore water temperatures may fluctuate by several degrees from the reported values, especially following heavy rainfall or extended periods of strong winds. Certain wind patterns can cause colder, deeper waters to rise and replace the sun-warmed surface water, leading to noticeable variations.
Our forecast is based on a proprietary mathematical model that considers real-time water temperature changes, historical trends, key weather patterns, wind strength and direction, and air temperature specific to each region. Additionally, we incorporate data from other resorts to enhance accuracy.
Water temperature data for this location is gathered from various sources, including buoys and satellite sea and ocean surface maps provided by the NOAA agency. We also incorporate data from local authorities in each specific location worldwide to ensure more accurate temperature readings.
Annual Water Temperature Overview by Month
Monthly Water Temp Ranges
Annual Water Temperature Trend
Marathon, in the middle of the Florida Keys, sits between the Atlantic Ocean and Florida Bay and enjoys a subtropical maritime climate that keeps surrounding waters mild year‑round. Seasonal surface temperatures typically range from about 22–25 °C in winter (December–February), warming to 23–27 °C in spring (March–May). Summer months (June–August) bring the warmest seas, generally around 27–31 °C, while autumn (September–November) usually holds temperatures near 25–29 °C as the water slowly cools. These averages can vary with weather patterns, tides and occasional upwelling, but overall Marathon’s water remains substantially warmer than most continental shorelines, making it a destination for extended water activities across many months.
Monthly Water Temperature Range (Min, Max & Average)
| Month | Min | Avg | Max |
|---|---|---|---|
| January | 19°C | 22°C | 26°C |
| February | 19°C | 23°C | 27°C |
| March | 20°C | 24°C | 28°C |
| April | 22°C | 26°C | 28°C |
| May | 24°C | 28°C | 32°C |
| June | 26°C | 29°C | 32°C |
| July | 27°C | 30°C | 34°C |
| August | 28°C | 31°C | 34°C |
| September | 27°C | 30°C | 33°C |
| October | 24°C | 29°C | 31°C |
| November | 21°C | 25°C | 28°C |
| December | 21°C | 24°C | 28°C |
* Click on a month to view detailed water temperature data.
Marathon: Weather Forecast
November 4
November 5
November 6
November 7
Location, Beaches & Local Information
Nearby Beaches & Facilities
Sombrero Beach
Coco Plum Beach
Key Colony Beach
Swimming Conditions
Swimming and beach holidays in Marathon take advantage of shallow bays, sandy shorelines and nearby coral reefs, offering options for casual beachgoing, snorkeling and open‑water swims. Public spots and small beaches provide safe, family‑friendly areas with gentle entry and calm water when winds are light, while boat access opens the offshore reef for clearer water and abundant marine life. The relatively high summer temperatures make long swims and snorkeling comfortable without heavy exposure protection, and even winter swims are feasible for many visitors at the lower end of the temperature range. Visitors should still monitor local conditions, including wind, currents and seasonal marine life, to choose the safest times and locations for swimming.