This is a pre-passage source and decision desk, not a current forecast or clearance to depart. The map is centred approximately on the area, not on your route or a forecast-zone boundary.
Resolve the exact named coastal and offshore forecast sectors before crossing a national boundary. Island lee, headland acceleration and a narrow channel can differ from a broad Mediterranean model cell.
1. Primary sources
Open current bulletins and warnings for every sea area on the route. These links are starting points, not a promise that each covers the whole location; if unsure, identify the issuer through WMO–IMO.
2. Route and local effects
Check wind acceleration in island gaps and the exposure of the arrival harbour.
Cyclades hops can alternate a sheltered departure with an exposed inter-island gap. Plot the actual gap and destination, not just the nearest island.
Compare the named HNMS Aegean sectors, timing of a northerly blow and the lee of the arrival island; a calm harbour report cannot clear an exposed channel.
How to use this source set
Start with the warning, then the marine text for the exact named area. If the route crosses a zone boundary, obtain both bulletins. Note issue and valid times, wind units and the meaning of wave height. Where a link opens an agency portal, navigate to its current marine product; a homepage is not itself a forecast.
Compare with an exposed station or buoy if available. Check its position and observation time: a sheltered station does not overturn a warning for an open channel. If a bulletin is missing or stale, identify the issuing service via WMO–IMO and defer the decision until current information is available.
Before-passage check
- Mark departure, exposed legs, arrival and feasible diversions; find the responsible named marine areas for each.
- Check warnings, issue and valid times; assess conditions when you expect to reach each leg, not only at departure.
- Compare wind and gusts, waves and swell, visibility, thunderstorms and local effects; do not infer a strait from a sheltered harbour.
- Compare recent observations where available, noting their time and exposure; a mismatch calls for another check.
- Set the next bulletin check, a reassessment trigger, an alternative and a backup communication channel.
Model map — optional
Windy is a third-party model display, not the issuer of official warnings. Choose a layer and check its valid hour and model run. Nothing loads until you click.
Without JavaScript, open the map separately.
If connectivity fails
Before departure, save the current official text bulletin and warning with issue time. Arrange another way to receive updates, such as an appropriate coastal broadcast, NAVTEX or satellite channel. A saved map cannot replace new warnings.
How to choose weather tools · All sailing areas
Scope: Source list assembled 25 September 2026; check its freshness and coverage before use. This public area guide is not a current personalised forecast, navigational notice service or safety verdict. Personalised forecasts with AI and experts are in closed testing; public booking is not open. The skipper makes the decision.
Local passage-planning dossier
Turn a Cyclades island list into a sequence of exposed gaps and workable arrival options.
Forecast sectors and coverage
Check the named HNMS Aegean sectors against your actual islands; one Central Aegean text may not describe an entire Lavrion–Cyclades itinerary. For the mainland departure, confirm the neighbouring coastal sector rather than selecting the nearest island name.
Weather-sensitive legs
Distinguish a passage along an island lee from a crossing between islands. With a northerly forecast, an outward and return leg can have different wind and wave angles. Do not assume that an anchorage suitable for the outbound direction remains suitable after a wind shift.
Observations, sea state and reassessment
Inspect the route-facing wave layer, not a harbour temperature forecast. Use POSEIDON observations where operating; check whether a measured low wind is from the lee. Refresh before committing to the next open-water gap.
Worked planning scenario — not a live forecast
For a two-leg island hop, calculate arrival at the second island rather than evaluating both legs at departure time. If a forecast shift occurs between them, compare a one-island stop with the original plan and specify when the second leg must be reconsidered.
Official products by task
- HNMS marine bulletin — Locate the named Greek sea sectors; check the actual issue, not a city forecast.
- HNMS sea-area warnings — Marine warning entry point; distinguish sea warnings from land alerts.
- HCMR POSEIDON monitoring tools — Find observing platforms and distinguish measurements from model fields; check gaps and timestamps.
Sector names help you locate the issuing product; they are not an automatic route-coverage match. Open the current issue and check boundaries, issue time and validity. This page does not display current warnings; an unavailable product does not mean no hazard.
Countries & territories
- Greece
Ionian coast, Saronic Gulf and open Aegean island passages require different plans.
Departure ports & bases
- Lavrion
Lavrion: a departure-source desk, not a generic city forecast.
Build your passage brief
Bring your route, leg timings, vessel and crew profile, checked sources and reassessment triggers into the brief. Personal AI analysis and expert review are available to invited closed-test participants; a port page does not extend the calculation service’s coverage.
A Sailing Weather editorial guide to local conditions, practical passage preparation and marine-weather sources. Source and structure review: 27 September 2026. For a specific passage, check current issues, validity and forecast coverage. The skipper retains the final decision and responsibility.
Outward and return passages are different products
On a Lavrion–Kea–Kythnos example, enter the actual channel headings and ETAs rather than treating the islands as one forecast point. An outbound downwind leg can leave the crew with a more demanding return after the next change. Compare the forecast at the turn-around time and final approach, not just the first hour; extending the island itinerary should trigger a new brief, not an extra pin on the same map.
- HNMS marine sectors — Named Greek sea sectors; not automatic route matching Direct product verification is limited; obtain the current issue from the issuer.
Wind shelter does not guarantee wave shelter
For the chosen arrival coast, draw the direction from which forecast wind waves and swell approach it. Assess the exposed cape before the bay as a separate leg. A lee-side anchorage may reduce local wind while still admitting swell through its entrance. POSEIDON can add measured or modelled marine context, but first identify which kind of layer you are reading and whether the record is recent.
- HCMR POSEIDON observing components — Greek marine observing infrastructure; operating status must be checked Direct product verification is limited; obtain the current issue from the issuer.
A useful cancellation rule
For a two-island day, define the latest time at which the second crossing can still be assessed with current sources and a viable arrival. If the first leg takes longer than planned, recalculate the second-leg exposure using the delayed ETA. Do not carry an earlier forecast window forward without checking its expiry. Prepare a one-island itinerary so shortening the day is a usable plan rather than an improvised failure.
- HNMS marine bulletin guide — Units, time terms, warning structure Direct product verification is limited; obtain the current issue from the issuer.
Editorial review of this material: 27 September 2026. This date concerns the page content; check current forecast issue times and validity at the original sources.