The best time to leave, and the weather all the way there.

Sea Window is the marine weather app for coastal trips of four hours to two days. It ranks departure times against your own limits, then shows the wind, seas, tide and current at every waypoint for the hour you'll be there.

See how it works

Ranked against your limits
Tidal currents included
GFS, ICON and ECMWF compared

Sea Window planning a trip from Newport to Block Island: the best window is to leave today at 09:00, rated good, arriving 13:32 with wind up to 13 knots and seas up to 2.0 feet all the way

Why 09:00 Inside your limits all the way

Wind up to 13 kn and seas up to 2.0 ft from Newport to Block Island.

GoodModels agreeTidal currents included

Departure Advisor

Departure times ranked against your own limits

Set the most wind, gusts and sea you're happy with, and the least visibility you'll accept. Sea Window tries a departure every 30 minutes across the next 72 hours, follows each one along your route and ranks them. The answer reads like a note from a skipper who has done the sums: when to leave, and the one condition that decides it.

Your limitsRelaxed, Moderate or Experienced, scaled to your boat type and length. Or set your own numbers.
CurrentsNOAA tidal-current predictions near your route in US waters and ocean-model currents elsewhere. Wind against current is called out.
The verdict"Leave Sat 07:00" with the reason: the windiest hour, the biggest seas, the strongest current, or wind and seas inside your limits all the way.
ConfidenceWhether GFS, ICON and ECMWF agree, and any official warning in force on the route.

How the Departure Advisor works

Best windowGood

Leave Sat 07:00

Arrive 13:20 at Block Island

Biggest seas around 11:00: 2.6 ft.

Leave after 10:00 and the wind runs against the current.

Along your route

Leave 07:00Arrive 13:20

ComfortableNear your limitOver your limit

Models agreeTidal currents includedNo warnings in force

The next 72 hours

Now+24 h+48 h+72 h

Each bar is one departure, coloured for the whole trip.

Route weather

The forecast at every waypoint, for the hour you'll be there

Draw your route and set your cruising speed. Sea Window works out when you'll reach each waypoint and pulls the forecast for that place at that hour. The whole passage reads as one timeline, so the breeze that fills in after lunch shows up on the leg where you'll meet it.

WindSpeed, gusts and direction, with apparent wind and your point of sail.
SeasHeight, period and direction, and how the ride will feel.
CurrentWith you, against you or setting you sideways, leg by leg.
SpeedChange your speed and every arrival time and forecast moves with it.

A weather map drawn for the water

Colour fields for wind, gusts, waves, swell, rain and pressure, with the coastline drawn on top, streaks that drift with the wind and arrows for the current. Slide through the next 48 hours and watch the breeze build along your route.

Forecast

Wind and gusts
Waves and swell
Rain
Pressure and isobars

Live

Rain radar
Lightning
Clouds
Buoys and stations

Ocean

Sea temperature
Chlorophyll
Bay and ocean model currents
Tidal-current stations

Context

Tropical storms from NHC
NWS warning areas
NOAA charts and OpenSeaMap
Depth contours and harbours

Explore the conditions map

Marine forecast

Everything you check before a trip, on one screen

Wind on a compass, the barometer with its three-hour trend in plain words, fog and squall outlooks, waves split into swell and wind wave, tides, and seven days hour by hour. Each day carries a badge that says whether GFS, ICON and ECMWF agree.

Weather screen with no official marine warnings for these waters, 54 °F and partly cloudy, sea 59.5 °F, 9.1 nautical miles visibility, wind 8.4 knots from the west gusting 17.1, and the barometer steady at 1025 hPa

Waves card: sea state 2, slight, 2.2 feet; total 2.2 ft at 5.7 seconds from the southeast, swell 2.2 ft at 4.8 seconds, wind wave 0.3 ft at 1.6 seconds from the northeast — **Swell and wind wave, apart**The total sea split into its parts, each with its period and direction.

Squall and thunderstorm card: stable atmosphere, low convective activity expected over the next 24 hours, peak CAPE 170 J/kg, minimum lifted index 3.0, peak risk none — **Squall risk, hour by hour**Convection signals for the next 24 hours, with the peak and when it comes.

Tides card for Beaufort, Duke Marine Lab, 0.3 nautical miles away, from NOAA CO-OPS on the MLLW datum: falling from 3.3 to 0.5 feet, next low in 5 hours 27 minutes at 19:09, the tide curve and the next four highs and lows — **Tides for your harbour**The nearest station, the curve and the next four turns, with the datum shown.

Tidal current card for the Radio Island station, 1.1 nautical miles away: slack water at 1:58 PM, in 16 minutes — **Tidal currents and slack water**The nearest NOAA current station: flood, ebb and the next slack.

See the full marine forecast

Warnings and live data

Official warnings, live buoys and the models behind every number

Sea Window collects the public marine feeds a careful skipper reads anyway, keeps them fresh on a timer, and puts them where they matter: on the forecast, on the map and in the departure ranking.

Source	What you get	Coverage
NWS marine warningsChecked every 3 minutes	Small craft advisories, gale and special marine warnings on a card and as areas on the map, with optional push alerts for your home waters.	US coastal and offshore waters
NWS zone forecasts	The forecaster's own text for the zone you're in.	US marine zones
NDBC and AODN buoysEvery 15 to 30 minutes	Measured wind, waves, pressure and water temperature, with 24 hours of history.	US and Australia
NOAA CO-OPS	Tide predictions, and current stations with flood, ebb and slack times.	US stations, model tides worldwide
GFS, ICON and ECMWF	The global models behind the 7-day hourly forecast and the agreement badge.	Worldwide
NOAA nowCOAST and NHC	Radar, lightning, clouds, bay and ocean model currents, and tropical storms.	US waters, Atlantic and eastern Pacific
NASA satellite imagery	Sea surface temperature and chlorophyll.	Worldwide
World Port Index	Harbours and their details on the map.	Worldwide

Made for the trip, not just the forecast

Saved plans and a logbook

Keep every route and check it again when the forecast changes. Record a trip to keep its track, distance, time and speed.

Works with no signal

Download map regions before you go. Your latest forecasts, tides and route weather stay on the phone for 24 hours.

Sun, moon and solunar

Sunrise, sunset, moon phase and the solunar periods anglers plan around, worked out on your phone.

Your units

Marine, US or Metric presets, or knots, feet, metres, Fahrenheit and Celsius set one by one.

Ten languages

English, Danish, German, Spanish, French, Italian, Dutch, Norwegian, Portuguese and Swedish.

iPhone and iPad

Your routes, trips and settings sync through your account. A layout built for the iPad screen is on the way.

Guides

Read the weather like a passage maker

Plain explanations of the numbers that decide a coastal trip, written for people who already know the sea.

Passage planning

How to find a weather window for a coastal passage

Turn a forecast into a window that covers the whole trip, including a slow arrival.

Tides and currents

Wind against tide: why the sea stands up

What an opposing current does to waves, and how to time an inlet or a headland around it.

Reading forecasts

How to read a marine forecast

Wind, gusts, seas, period, visibility and pressure trend, and what each one means on the water.

Waves

Swell vs wind waves

Two kinds of sea, how they add up, and why the same height can feel completely different.

All guides

Questions boaters ask

What is Sea Window?

Sea Window is a marine weather app for iPhone and iPad, built for coastal boaters. It ranks the best times to leave over the next 72 hours against your own limits, shows the forecast at every waypoint of your route for the time you'll reach it, and puts wind, waves, tides, currents, fog, squall risk, official warnings and a 7-day marine forecast in one place.

Who is Sea Window for?

Coastal cruising sailors and power cruisers, trawlers included, on trips of four hours to two days: long enough for the weather to change along the way. Saltwater anglers and small-boat sailors use it for waves, tides, currents and fog too.

How does the Departure Advisor choose when to leave?

It tries a departure every 30 minutes for the next 72 hours. For each one it follows your route at your speed and checks wind, gusts, seas, visibility, thunderstorm risk and tidal currents at every point for the time you'd be there, including wind against current. Any leg over your comfort limits marks that departure rough. The best window comes first, with the one condition that limits it and what changes if you leave later.

How does route weather work?

Draw a route on the map and set your cruising speed. Sea Window works out your arrival time at every waypoint and fetches the forecast for that place at that hour: wind and gusts, seas and their period, visibility and current.

Where does the data come from?

Weather and sea forecasts come from the ECMWF, ICON and GFS global models. Tides and tidal currents come from NOAA CO-OPS stations in US waters and a global tide model elsewhere. Warnings and zone forecasts come from the National Weather Service, buoys from NDBC and the Australian Ocean Data Network, radar, lightning and model currents from NOAA nowCOAST, tropical storms from the National Hurricane Center, and sea temperature and chlorophyll from NASA satellites. Maps come from Mapbox, with NOAA charts, OpenSeaMap seamarks and GEBCO depth contours as layers.

Does it work outside the US?

Yes. Forecasts, waves, route weather, the Departure Advisor and the conditions map cover the world's coasts. Tides come from NOAA stations in US waters and from a global tide model everywhere else, and Australian buoys are on the map. Official warnings and zone forecasts are from the US National Weather Service.

Does it work without a signal?

Download map regions before you go. Your latest forecasts, tides and route weather stay on your phone for 24 hours, so they're there when the signal drops, and they refresh on their own when you're back in range.

Can I use knots, feet or Fahrenheit?

Yes. Pick Marine (knots, °C, metres and nautical miles), US (knots, °F, feet and nautical miles) or Metric (km/h, °C, metres and kilometres), or set wind, temperature and heights one by one.

Is Sea Window on Android?

Sea Window is for iPhone and iPad. An Android version is planned.

Do I need an account?

Yes. Sign in with Apple, Google or email so your routes, trips, limits and settings follow you between devices. You can delete your account from the app at any time.

Pick your window before you cast off

Your route, your limits and the next 72 hours, ranked in seconds.