Plan Athens/Piraeus–Aegina–Poros legs separately from open-Cyclades crossings.
Forecast sectors and coverage
Locate Saronikos and any adjacent HNMS sector for the actual track. A plan continuing toward the Cyclades needs additional sectors; the Athens city forecast is not the marine text.
Weather-sensitive legs
Separate marina exit, the open gulf and the island approach. The coast’s apparent shelter is direction-dependent; inspect the forecast direction at the destination rather than relying on the region’s cruising reputation.
Observations, sea state and reassessment
Find a representative available POSEIDON observation and compare its timestamp/exposure with the forecast. No nearby measurement is a gap; do not borrow an island lee observation as proof for the middle of the gulf.
Worked planning scenario — not a live forecast
For Athens–Aegina, compare the gulf ETA and return timing under two departure options. If extending to Poros, add a separate leg and reassessment point instead of treating the whole day as one short crossing.
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.
Map orientation
The approximate map centre is not an approach waypoint, track, depth survey or forecast-zone boundary. The third-party map loads only on request.
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.
Give each extension its own coverage check
An Athens–Aegina day, an onward Poros leg and a continuation toward the Cyclades should be three planning cases. Locate Saronikos in the HNMS product and add adjacent sectors only where the plotted route actually enters them. Forecast names can be retained in Greek or official transliteration alongside an English/Russian explanation. The mainland city's forecast is not a substitute for that sector selection or its valid time.
- HNMS marine sectors — Named Greek sea sectors; not automatic route matching Direct product verification is limited; obtain the current issue from the issuer.
A sheltered start can hide the return problem
Put the open gulf, cape or channel and the final marina approach on the timetable. For a round trip, compare the outward and return wind/wave angles using their different ETAs. The relevant sea state may persist after the wind declines. Use POSEIDON only after identifying whether the selected layer is a forecast or a measured record; the nearest platform need not represent the intended approach.
- 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.
Brief a delay rather than improvising it
For an Aegina visit, set a reassessment before extending the shore stop or adding another island. Recalculate the return ETA if the visit overruns and check whether the current bulletin still spans arrival. A prepared shorter circuit gives the crew a useful alternative without suggesting any bay is universally sheltered. Obtain separate harbour information for access and services; this source desk makes no berth or anchoring guarantee.
- 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.