Marine Weather API
Part of the Foreca Weather API: wave, swell and sea temperature forecasts that tell your users what the water is like before they head out.
Waves, swell and sea temperature for all seas and oceans
Hourly up to 7 days · daily up to 10 days
Included in the Cumulus plan · free 30-day trial
Built for life on and by the water
From sailing and surf apps to beach guides and coastal tourism, marine forecasts help wherever the sea shapes the plans.
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Boating and sailing apps: show waves and wind together so your users can pick the right day and route for a trip.
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Surf apps: show the swell, how often it arrives and where it comes from, so surfers know when the waves are worth the drive.
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Beach, travel and coastal tourism: tell holidaymakers and tour operators how warm and how rough the sea will be, days before the trip.
Marine Weather API at a glance
The Cumulus plan includes Marine Weather API. Explore the included features below.
Waves
Significant wave height, period and direction, with swell and wind waves separately.
Sea temperature
Sea temperature and Foreca's estimate of the water temperature for swimming.
Wind
Wind speed, gusts and direction from Point Forecasts in the same plan, also in knots.
Forecast length
Hourly up to 7 days. Daily up to 10 days for waves and 15 days for sea temperature.
Coverage
All seas and oceans and the largest lakes.
Resolution
Waves on a grid of about 14–28 km, sea temperature about 9 km.
Method
Global weather and wave models processed by Foreca. Waves update twice a day, sea temperature four times a day.
Format
REST API, JSON. Query by coordinates or Foreca location ID.
How your app gets the data
Two calls cover most apps: an hourly forecast for the detailed view of the coming days, and a daily forecast with each day's highest waves and warmest sea for a quick overview.
What it works best for
Planning a day on or by the water: when the sea is calm enough to go out, when the swell is right for surfing and when the water is warm enough to swim.
Combine with wind forecasts
Show waves and wind side by side. Point Forecasts (included in every Foreca Weather API package) gives the wind speed, gusts and direction for the same location, so your users see the full picture for a day on the water.
What the marine forecast shows
Each hour of the forecast describes the waves and the water at one location.
Example: Hanko, Finland, 29 October 2026 at 13:00
| Value | What it shows | Hanko, 13:00 |
|---|---|---|
| Significant wave height | Typical height of the larger waves | 0.71 m |
| Wave period | Average time between waves | 4.3 s |
| Wave direction | Where the waves come from | 202° (SSW) |
| Swell | Waves that have travelled from far away: height, period and direction | 0.69 m · 4.3 s · 201° |
| Wind waves | Short waves raised by the local wind: height, period and direction | 0.10 m · 1.5 s · 254° |
| Peak period | Period of the waves that carry the most energy | 4.8 s |
| Sea temperature | Temperature of the sea surface | 10 °C |
| Swimming temperature | Estimated water temperature for swimmers | 10 °C |
Marine Weather API FAQ
Will single waves be as high as the forecast?
No. Significant wave height is the average height of the highest third of the waves. Single waves can be up to about twice as high, so a forecast of 1 m can bring single waves of nearly 2 m.
Does the forecast cover lakes?
Only the largest ones. Waves come for all seas and oceans, including the Baltic Sea, and for the largest lakes, such as the Great Lakes, the Caspian Sea and Lake Victoria. Smaller lakes, such as Lake Geneva, get no waves.
What happens if I ask for a location on land?
You get a normal response, but the wave values are empty (null). Sea and swimming temperatures still have a value, but on land it does not describe real water, so make sure the location is at sea or on the coast. Coastal locations get waves.
How is swimming temperature different from sea temperature?
Swimming temperature is Foreca's own estimate of the water temperature for swimmers, and it can differ slightly from the sea temperature. You get it everywhere the sea temperature is available. On a frozen sea, it is 0.
Does Marine Weather include tides or currents?
No. Marine Weather has no tide or current data.
Can I get wave heights in feet?
No. Wave heights always come in metres, so convert them in your app (1 m = 3.28 ft). Sea and swimming temperatures come in °C or °F, as you choose, in whole degrees.
Can I show my users the sea over the last 24 hours?
Yes. The hourly forecast can start 24 hours back. The past hours are forecast model values, not measurements, and they count toward the number of hours you ask for.
I only need sea temperature maps. Which plan do I need?
The Stratus plan. It includes Weather Maps with every map layer, also sea temperature, as well as Point Forecasts and Air Quality. The sea temperature layer also colours land areas, so put a land or base map layer on top. There is no wave map layer.
Start building with marine forecasts
Read the Marine Weather documentation for the hourly and daily calls, and the Weather Maps documentation for the sea temperature map layer.
Try it first: the 30-day free trial includes Marine Weather, with 2,000 requests a day and no credit card.