Rainfall

Rainfall is the forecast or observed amount of rain expected over the sea or at a coastal location during a set period, usually expressed in millimetres. In marine forecasting it indicates where precipitation bands, showers or fronts may affect a vessel’s route, anchorage or harbour approach.

For boaters, rainfall matters because heavy rain can reduce visibility, obscure marks and traffic, make decks slippery, and accompany squalls or wind shifts. Persistent rain can also affect comfort, watchkeeping and electrical reliability on passage. Check rainfall alongside Cloud Cover, Wind Gust and Sea State to judge whether conditions are merely wet or operationally hazardous.

PredictWind rain maps and GRIB forecasts help crews compare timing, intensity and coverage between models such as ECMWF, GFS and ICON. Offshore users can download rainfall layers in the Offshore App via satellite to monitor fronts and convective showers while underway.