Separate sea-facing approaches, estuary sectors and managed inland waters.
Forecast sectors and coverage
Use the relevant KNMI sector such as Flushing or Zierikzee after checking its definition. The precise waterway matters; Zeeland is not one identical tidal basin or a single forecast point.
Weather-sensitive legs
List the sea entrance, tidal estuary and lock/bridge connections separately. Wind, tide and navigation constraints can affect them differently; check the actual waterway rather than inferring all conditions from a regional map.
Observations, sea state and reassessment
RWS levels require a named station and datum; do not combine a measured level at one basin with chart depths or tidal timing from another. Verify current waterway and harbour notices independently.
Worked planning scenario — not a live forecast
For a sea-to-inland day, compare the entrance ETA and the final lock connection under both departure options. If the route changes basin, refresh the water-level source instead of keeping the first station throughout.
Official products by task
- KNMI coastal waters — Named Dutch coastal, estuary and lake sectors; issue and validity are shown at the issuer.
- Rijkswaterstaat Waterinfo — Water levels and available water observations; check station, units and datum before comparison.
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
- Netherlands
Distinguish North Sea/Wadden, inland lakes and Zeeland waterways before choosing data.
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.
Name the basin before choosing a forecast
Westerschelde, Oosterschelde and managed inland waters should not receive one identical Zeeland weather/tide brief. Specify the actual basin and connections, then select the relevant KNMI coastal/estuary sector. Keep a sea-facing entrance separate from a protected-water leg and a lock transfer. A regional weather map may be useful for wind evolution, but it does not establish the stream, water level or usable route inside every basin.
- KNMI coastal waters, lakes and estuaries — Named Dutch sectors including IJsselmeer and Marken; read actual issue/validity.
- Rijkswaterstaat Waterinfo — Water observations and forecasts; parameter, station and datum must be checked. Direct product verification is limited; obtain the current issue from the issuer.
Do not carry one gauge through every lock
For each water-level check, retain station, reference and measured-versus-predicted status. When a lock changes the water body, reconsider which series remains applicable. Do not combine the measured level of one estuary with depths or timings from another. Check current authority notices for lock, bridge and traffic constraints as independent evidence; a weather product is not an operational notice service.
- Rijkswaterstaat Waterinfo
- Rijkswaterstaat IJsselmeer water information — Official lake information and links to water data and waterway/lock notices.
A sea-to-lake itinerary has two clocks
Compare departure options against the sea entrance's local constraints and the confirmed inland connection, with an allowance for slower progress. If the entrance becomes unfavourable or a connection is missed, reassess the nearest feasible refuge before committing to the exposed leg. Improving the offshore wind while creating an unworkable final lock arrival is not an improvement of the whole itinerary.
- KNMI coastal waters, lakes and estuaries
- RYA passage planning — Practitioner guidance on contingency, tides, vessel and crew constraints.
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.