Onset water temp
This data the coastal Onset 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 Onset
Water temperature in Onset today is 66.6°F. Based on our historical data over a period of ten years, the warmest water in this day in the Atlantic Ocean near Onset was recorded in 2021 and was 71.4°F, and the coldest was recorded in 2020 at 63.9°F. Sea water temperature in Onset is expected to drop to 64.6°F in the next 10 days. September average water temperature in Onset is 68.5°F, the minimum temperature is 63.1°F, and the maximum is 77°F.
The swimming season in Onset lasts from July to September. During those months, Onset water temperature does not drop below 68°F and therefore suitable for comfortable swimming. The average water temperature in Onset in winter reaches 39.9°F, in spring 46.2°F, in summer the average temperature rises to 69.1°F, and in autumn it is 61°F.
Onset water temperature now
| September 25, 2025 |
|---|
| today temp |
| 66.6°F |
| September 24, 2025 |
|---|
| yesterday temp |
| 66.6°F |
The ocean salinity in Onset is 28.85‰, and the average salinity of the World Ocean is 35‰.
Surf Forecast in Onset 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 Onset. 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 Onset. Data in table shown for September 25, 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' 7" | 0' 7" | 0' 6" | 0' 7" |
| 0.18 m | 0.17 m | 0.16 m | 0.17 m |
| 12-15 h | 15-18 h | 18-21 h | 21-24 h |
|---|---|---|---|
| 0' 11" | 1' 3" | 1' 6" | 1' 8" |
| 0.27 m | 0.38 m | 0.45 m | 0.51 m |
Surf report in Onset
Onset weather forecast
Current temperature and weather
Data in a table show Onset temperature today (September 25, 2025). For more information and forecast for a few days, go to the weather forecast Onset.
| 0-3 h | 3-6 h | 6-9 h | 9-12 h |
|---|---|---|---|
 | | | |
| 63.3°F | 63.3°F | 63.7°F | 66.9°F |
| 12-15 h | 15-18 h | 18-21 h | 21-24 h |
|---|---|---|---|
 | | | |
| 69.3°F | 70°F | 70.3°F | 70.2°F |
You may also be interested in other sections of our site for Onset: Sunrise and Sunset, Tides
Onset water temperature by month
These figures shows the average, minimum and maximum monthly sea temperature in Onset. 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 Onset 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 | 38.8°F | 31.8°F | 46.4°F | cold |
| Ocean water temperature in Onset in January | ||||
| February | 36.5°F | 31.3°F | 45°F | cold |
| Ocean water temperature in Onset in February | ||||
| March | 39°F | 32°F | 47.8°F | cold |
| Ocean water temperature in Onset in March | ||||
| April | 45.5°F | 36.5°F | 54.3°F | cold |
| Ocean water temperature in Onset in April | ||||
| May | 54.3°F | 47.1°F | 64°F | cold |
| Ocean water temperature in Onset in May | ||||
| June | 63.7°F | 55.8°F | 75.4°F | cold |
| Ocean water temperature in Onset in June | ||||
| July | 71.2°F | 62.6°F | 78.8°F | warm |
| Ocean water temperature in Onset in July | ||||
| August | 72.3°F | 65.5°F | 79.7°F | warm |
| Ocean water temperature in Onset in August | ||||
| September | 68.5°F | 63.1°F | 77°F | warm |
| Ocean water temperature in Onset in September | ||||
| October | 61.7°F | 54.9°F | 67.5°F | cold |
| Ocean water temperature in Onset in October | ||||
| November | 52.5°F | 43.2°F | 60.6°F | cold |
| Ocean water temperature in Onset in November | ||||
| December | 44.4°F | 35.8°F | 52°F | cold |
| Ocean water temperature in Onset in December | ||||
Chart monthly average water temperature in Onset
