Grassy Key water temp
This data the coastal Grassy Key ocean 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 ocean temperature in Grassy Key
Water temperature in Grassy Key today is 86.2°F. Based on our historical data over a period of ten years, the warmest water in this day in Grassy Key was recorded in 2022 and was 87.1°F, and the coldest was recorded in 2012 at 83.3°F. Sea water temperature in Grassy Key is expected to drop to 84.2°F in the next 10 days. September average water temperature in Grassy Key is 85.6°F, the minimum temperature is 82.9°F, and the maximum is 88.9°F.
The swimming season in Grassy Key lasts from January to December, twelve months per year! During those months, Grassy Key water temperature does not drop below 68°F and therefore suitable for comfortable swimming. The average water temperature in Grassy Key in winter reaches 76.1°F, in spring 78.8°F, in summer the average temperature rises to 85.6°F, and in autumn it is 82.9°F.
Grassy Key water temperature now
| September 26, 2025 |
|---|
| today temp |
| 86.2°F |
| September 25, 2025 |
|---|
| yesterday temp |
| 85.8°F |
Surf Forecast in Grassy Key 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 Grassy Key. 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 Grassy Key. Data in table shown for September 26, 2025, time in GMT 0 format (you can change the time zone on the sea state forecast page)
| 0-3 h | 3-6 h | 6-9 h | 9-12 h |
|---|---|---|---|
| 0' 9" | 0' 9" | 0' 9" | 0' 8" |
| 0.24 m | 0.23 m | 0.22 m | 0.21 m |
| 12-15 h | 15-18 h | 18-21 h | 21-24 h |
|---|---|---|---|
| 0' 8" | 0' 7" | 0' 7" | 0' 7" |
| 0.2 m | 0.19 m | 0.18 m | 0.17 m |
Surf report in Grassy Key
Grassy Key weather forecast
Current temperature and weather
Data in a table show Grassy Key temperature today (September 26, 2025). For more information and forecast for a few days, go to the weather forecast Grassy Key.
| 0-3 h | 3-6 h | 6-9 h | 9-12 h |
|---|---|---|---|
 | | |  |
| 82.4°F | 82°F | 81.9°F | 83.3°F |
| 12-15 h | 15-18 h | 18-21 h | 21-24 h |
|---|---|---|---|
| | | |
| 84.9°F | 84°F | 83.5°F | 83.1°F |
You may also be interested in other sections of our site for Grassy Key: Sunrise and Sunset, Tides
Grassy Key water temperature by month
These figures shows the average, minimum and maximum monthly sea temperature in Grassy Key. 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 Grassy Key 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
| Month | Avr | Min | Max | |
|---|---|---|---|---|
| January | 75.4°F | 70°F | 80.2°F | warm |
| Ocean water temperature in Grassy Key in January | ||||
| February | 75.4°F | 69.8°F | 79.5°F | warm |
| Ocean water temperature in Grassy Key in February | ||||
| March | 76.3°F | 71.1°F | 80.6°F | warm |
| Ocean water temperature in Grassy Key in March | ||||
| April | 78.6°F | 74.1°F | 83.3°F | hot |
| Ocean water temperature in Grassy Key in April | ||||
| May | 81.5°F | 77.7°F | 86.7°F | hot |
| Ocean water temperature in Grassy Key in May | ||||
| June | 84.2°F | 79.3°F | 87.4°F | hot |
| Ocean water temperature in Grassy Key in June | ||||
| July | 86°F | 82.9°F | 89.8°F | hot |
| Ocean water temperature in Grassy Key in July | ||||
| August | 86.5°F | 83.3°F | 90°F | hot |
| Ocean water temperature in Grassy Key in August | ||||
| September | 85.6°F | 82.9°F | 88.9°F | hot |
| Ocean water temperature in Grassy Key in September | ||||
| October | 83.3°F | 78.6°F | 86.4°F | hot |
| Ocean water temperature in Grassy Key in October | ||||
| November | 79.9°F | 76.1°F | 83.8°F | hot |
| Ocean water temperature in Grassy Key in November | ||||
| December | 77.5°F | 73°F | 81°F | hot |
| Ocean water temperature in Grassy Key in December | ||||
Chart monthly average water temperature in Grassy Key
