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Learn how forecasts, warnings, buoys and tide information help describe conditions on the water.
Marine forecasts describe wind, waves and weather for a named area of water. A forecast for a nearby town may not describe conditions offshore. Find the forecast zone that includes your planned area, then read the periods covering both departure and return. Check wind direction, sustained wind and gusts, wave height and the chance of storms or fog. Conditions can differ near shore, in an inlet or behind a headland. A regional forecast cannot describe every sheltered or exposed spot.
Marine warnings describe particular hazards. Their names are not interchangeable. A Special Marine Warning addresses short-lived hazards such as strong thunderstorm winds, large hail or waterspouts. Gale, storm and tropical warnings concern other specified wind threats. A Small Craft Advisory depends on local criteria; there is no single boat size that makes an advisory harmless. Read the full message and its affected area. No warning does not mean every boat or outing is safe.
A buoy report is a measurement, not a promise about the conditions you will encounter. Check the station location, measurement time and units. Missing wind or wave readings mean that information is unavailable, not that the wind or water is calm. Significant wave height is approximately the average height of the highest third of the waves; individual waves can be higher. Wave period also matters: waves of the same height can be much steeper when they arrive closer together.
Tides describe changing water levels. Tidal currents describe water moving horizontally. Use a station and product suited to the location. Tide predictions do not include every effect of wind, storms or river flow, so observed water levels can differ. High or low tide does not necessarily occur at slack current. Check the time zone, units and height reference before comparing readings; heights measured from different reference levels are not directly interchangeable.
An old observation or an earlier forecast may miss a developing storm or worsening wind. Check the observation time, forecast issue time and valid period separately. Refresh before departure and keep a way to receive marine weather updates while on the water. A phone connection may not be available offshore. Select a weather information source appropriate to your location and equipment, and know how you will receive warnings.
A weather page cannot confirm that a vessel, crew or route is ready for a trip. Use current charts and local information, wear an appropriate life jacket and leave a float plan with someone ashore. The person responsible for the vessel must consider its limits and the crew’s ability, and follow closures and local instructions. This guide explains weather products; it does not authorize departure or provide navigation directions.