Marine Weather Apps Compared: 6 Tested at Sea
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Most marine weather apps compared online are ranked by people who have never tried to load a GRIB file on 30 kbps of crew WiFi. That changes the answer completely. On a ship, the best forecast app is the one that downloads something small, keeps it offline, and still shows you wind and swell when the satellite link drops mid-refresh. Below is how six of the common ones behave under those conditions, what each costs as of August 2026, and which three actually earn a spot on your phone.
Quick answer for anyone in a hurry. Windy is the best all-round free option if you have decent bandwidth. PredictWind is the strongest for offline GRIB downloads on a metered link. Windfinder is the fastest thing to check before a shore-leave run. The other three have narrower uses, and one of them I would not install at all on a work phone.
Why ship conditions break normal weather apps
Weather apps assume broadband. That assumption fails at sea in three specific ways, and understanding them tells you what to look for.
The first is payload size. A modern weather app front page is a live map with animated particle layers, and that can pull several megabytes before it shows you a single number. On a shared crew connection at anchor, with twenty people streaming, that request times out. The app then shows a stale cache with no warning, which is worse than showing nothing.
The second is the refresh model. Many apps fetch on open and have no concept of "download now, read later". If you open it in the mess where the WiFi reaches and then walk to your cabin, you get a spinner. The apps worth having let you pull a forecast package deliberately and keep it.
The third is time and position. Ship time drifts from UTC and from local zone constantly, and phone GPS inside a steel accommodation block is unreliable. An app that silently uses your last known position can show you the weather for a port you left two days ago. Any app that lets you pin a manual lat/long or a named waypoint solves this. Most consumer apps do not.
There is a separate point worth saying plainly. None of this replaces the bridge. The official forecast for navigation comes through NAVTEX, Inmarsat SafetyNET and the ship's routing service, and that is the source that matters for the passage plan. What follows is for personal use: knowing whether tomorrow's deck work gets cancelled, whether your shore leave window survives, whether the pilot boarding will be a wet one.
Marine weather apps compared: the table
Here is the short version across the six, with pricing checked in August 2026. Subscription prices move, so treat these as ballpark and check the app store listing before you pay.
| App | Free tier | Paid tier (approx, Aug 2026) | Offline forecasts | Wave and swell data | Works on slow link |
|---|---|---|---|---|---|
| Windy | Full map, most models | Premium around 20 to 25 USD/year | Weak, map tiles cache only | Yes, swell height, period, direction | Poor on first load, fine after |
| PredictWind | Limited forecasts, 1 location | Standard and Professional, roughly 20 to 50 USD/month range | Strong, GRIB download by area | Yes, plus multiple model comparison | Good, GRIB files are small |
| Windfinder | Spot forecasts, ads | Plus around 15 to 20 USD/year | Partial, last-loaded spot | Yes on coastal spots | Very good, lightweight pages |
| Ventusky | Full map | Premium around 10 to 15 USD/year | No meaningful offline | Yes, wave layer | Moderate |
| NOAA / national met apps | Free | None | Text products cache well | Varies by region | Excellent for text bulletins |
| MyRadar | Full radar, ads | Around 10 to 20 USD/year to remove ads | Radar only, short window | Limited | Coastal only, useless offshore |
Read that table with one thing in mind. The "works on slow link" column is the one that decides whether you keep the app after month one.
Windy: the default, with a caveat
Windy is the app most crew end up using, and it deserves that position for one reason: it shows several forecast models side by side. Being able to flip between ECMWF and GFS for the same 48 hours tells you something no single-model app can, which is how confident the forecast actually is. When the two models disagree on wind direction for tomorrow afternoon, you plan for both.
The swell layer is genuinely useful for anyone doing deck work or expecting a pilot transfer. You get significant wave height, period and direction, and the period number is the one people ignore. Eight-second swell at two metres and fourteen-second swell at two metres are two completely different days on a pilot ladder.
The caveat is weight. Windy is built as a live map, and that first load is heavy. On a bulk carrier's crew connection I have watched it sit at a blank blue screen for a full minute before anything renders. Once cached it behaves, but if you have not opened it in a week you are starting from scratch. If your ship's link is the kind described in what internet on bulk carriers actually delivers, open Windy while you still have signal, not when you need the answer.
Premium adds one-hour forecast steps and removes the ad, and as of August 2026 it sits around 20 to 25 USD a year. That is fair value if Windy is your main app. Check the current price in the app before subscribing.
PredictWind: the one built for metered connections
PredictWind is the only app in this group designed from the start for people with expensive, slow satellite data. That shows in the one feature that matters most offshore: you select an area, choose a resolution, and it downloads a compressed GRIB file you can then read with the connection off.
A GRIB covering a few hundred nautical miles at a coarse resolution is tiny compared to a map page. That is the whole trick. You are downloading numbers, not pictures, and your phone draws the picture locally. On a link where Windy times out, a GRIB pull finishes.
PredictWind also runs its own models alongside the public ones and lets you compare four at once. For anyone actually interested in whether a forecast is trustworthy, that comparison is the useful part.
The honest problems are two. It is expensive, with the paid tiers running from roughly 20 up to 50 USD a month depending on which package and how many downloads you need, so check the current plans page before committing. And the interface is built for yacht racers and offshore sailors, so there is a learning curve if all you want is "will it rain in Rotterdam". If you are on a personal budget and never leave coastal waters, this is not your app.
Windfinder: the five-second check
Windfinder is the fastest app here for one specific question, which is what the wind is doing at a named coastal spot right now and over the next two days. Pages are light, they load on almost nothing, and the layout has not changed much in years, which on a slow connection is a compliment.
It is built around spots rather than a map, and most commercial ports have one. Before a shore-leave run I check Windfinder because it answers in five seconds without loading a map engine. If you are already building a pre-departure routine, it slots naturally next to the rest of the shore leave tech checklist.
The weakness is offshore coverage. Windfinder is a coastal and inshore tool. Once you are a few hundred miles out its spot model has nothing useful to say, and you should be looking at a GRIB instead.
Ventusky: beautiful, and that is the problem
Ventusky renders weather better than anything else on this list. The animation is genuinely clear, the wave layer is readable at a glance, and switching between parameters is fast once loaded.
That rendering quality is exactly why it struggles on a ship. It is a graphics-first app on a bandwidth-starved connection. It also has no real offline story, so a Ventusky screenshot is more useful than the app itself when you walk away from the WiFi.
Where it earns its place is in port with decent local data on your own eSIM. If you have a working local connection through something like the setups covered in what actually works for eSIM data between port calls, Ventusky is a pleasant way to read a forecast. Airalo installed ahead of arrival is the one I use for that, so the app has a real connection the moment you are ashore instead of fighting the anchor watch. On crew WiFi at anchor, less so.
National met service apps: free and underrated
Free national weather service apps are the most reliable thing on this list, because they serve text. The US NOAA marine products, the UK Met Office shipping and inshore forecasts, and their equivalents in most maritime nations publish plain-language coastal and offshore bulletins that load on almost any connection.
Text has a property no map has. It compresses to nothing, it renders instantly, and it stays readable in a screenshot. A coastal waters forecast bulletin is a few kilobytes. You can pull it on a link that cannot open a homepage.
The limitations are real. Coverage is national, so you are switching sources as you move between regions, and the offshore text products are written for a wide area rather than your exact position. But for zero cost and near-zero bandwidth, having the relevant national marine bulletin bookmarked is the single highest-value thing on this page.
MyRadar and the general-purpose apps: mostly skip
MyRadar and the general consumer weather apps are built for people who drive to work. Radar is a land product. It comes from ground stations, and coverage falls away fast once you are offshore, which makes a radar-first app close to useless beyond the coastal band.
There is also a privacy point that applies to the whole free-with-ads category. Many of these apps are funded by location data, and continuous background location on a work phone is a bad trade for a rain map. If you install one, set location permission to "while using" and turn off background refresh.
For the same storage you could carry a GRIB reader. That is a better use of the space, and the reasoning is the same as in the wider look at the apps that earn space on a marine engineer's phone.
Honest cons across the whole category
Every app here shares problems that no review usually mentions, so here they are plainly.
Forecast models are the same underneath. Windy, Ventusky and most others are drawing the same GFS and ECMWF data. The differences you are paying for are presentation, resolution steps and download options, not better weather knowledge. If two apps disagree, it is usually because they are showing different models or different run times, and neither is more correct.
Nothing here is a safety product. These are consumer apps with no service guarantee. The forecast that governs the ship's passage comes from the routing service and the official broadcasts. Treat everything on your phone as background information.
Offline modes are mostly marketing. Apart from PredictWind's GRIB download and the text bulletins, "offline" usually means "we cached what you last looked at, and we will show it to you without telling you how old it is". Always check the run time on the forecast before you trust it.
Position accuracy fails inside steel. GPS in a cabin below decks is unreliable, and an app that quietly falls back to your last fix can be a full day and several hundred miles wrong. Pin locations manually where the app allows it.
Subscriptions renew when you are not looking. A six-month contract is long enough to forget an annual renewal. If you subscribe for one season, set the reminder when you sign up.
Who should not bother with a paid weather app
Skip the paid tiers entirely if you fall into one of these groups.
If you work coastal and short-sea, the free national met bulletin plus free Windfinder covers everything you need, and the paid features are aimed at problems you do not have.
If your ship has Starlink and you have real bandwidth in your cabin, free Windy already does what the premium apps do, because your constraint was never the app. Living with that kind of link changes the whole calculation, which is covered in the honest look at Starlink Maritime for crew.
If you only want to know whether shore leave will be wet, any free app answers that. Do not pay for model comparison you will never open.
The people who should pay are the ones planning small-boat passages, doing weather-dependent deck operations they can influence, or working on vessels where the crew link is metered and slow. That is where PredictWind's download model earns its price.
How I would set it up on a work phone
Install two apps, not six. One lightweight checker and one download-based forecast tool cover every real situation, and the rest is duplication that eats storage and battery.
Bookmark the national marine bulletin for your current trading area in the browser, because it costs nothing and works when everything else times out. Pull your forecast deliberately while you are standing where the signal is good, and check the model run time before you act on it. Set location permissions to "while using" for anything ad-supported.
That is the whole system. It takes ten minutes to set up at the start of a contract and then works for six months.
FAQ
Which marine weather app works best with no internet?
PredictWind is the strongest genuine offline option, because it downloads compressed GRIB files that your phone reads locally without a connection. Text bulletins from national met services are the free alternative, since they are small enough to load on almost any link and stay readable in a screenshot. Most other apps only cache what you last viewed, which is not the same thing.
Are paid marine weather apps worth it for crew?
For most crew on commercial vessels, no. The forecast that matters for navigation comes from the ship's routing service and official broadcasts, and free apps cover personal planning fine. Paid tiers earn their money if you are on a slow metered link and need repeated GRIB downloads, or if you plan weather-dependent operations yourself.
Can I trust a phone weather app for wave height at sea?
Treat it as an estimate, not a measurement. Wave data in consumer apps comes from the same global models everyone uses, and it is smoothed over a wide grid, so local conditions near coasts, in shallows and around currents can differ noticeably. Look at wave period as well as height, because a long-period swell at the same height behaves very differently on deck.
Why does my weather app show the wrong location on the ship?
Because GPS inside a steel accommodation block is unreliable and the app falls back to your last known fix. That fix can be days and hundreds of miles old, and most apps do not warn you. Pin the location manually by port name or coordinates in any app that allows it.
How much data does a marine forecast actually use?
A coarse GRIB file covering a few hundred nautical miles is typically a few tens of kilobytes to a few hundred, and a text bulletin is smaller still. A live weather map with animated layers can pull several megabytes on first load. That gap is why download-based apps work on ship connections and map-first apps do not.
Verdict
Two apps and a bookmark solve this for almost everyone. Take Windy for the model comparison and the swell layer, add PredictWind only if your link is slow and metered enough to justify it, keep Windfinder or your national met bulletin for the quick pre-shore-leave check, and delete the rest. The main thing to carry away from having these marine weather apps compared under real ship conditions is that download size beats features every time your connection is the weak link.
About the author
I am a working marine engineer and I have spent contracts on bulk carriers and tankers where the crew connection ranged from a metered satellite trickle to Starlink in the cabin. Everything above comes from using these apps in those conditions, checking forecasts before deck work and shore leave, and watching which ones actually load when the link is under load. Where I have given a price it is a ballpark as of August 2026, so confirm it on the official page before you subscribe. I have no commercial relationship with any of these apps.