How the predictions work

River cruises fail at specific places: the shallow, free-flowing stretches a ship must pass. We model 9 of those choke points directly rather than averaging a whole river: the Rhine gorge at Kaub, the Straubing to Vilshofen reach and the Wachau on the Danube, the Elbe at Dresden, the Seine through Paris.

Four sources, all official or public. Live water levels come from the national gauge networks (Germany's WSV PEGELONLINE and France's Vigicrues), read daily. History is thirty years of daily flow records from GloFAS, the EU's river-monitoring system. The forward look is GloFAS's forecast, which runs about seven months ahead. Because rivers are made of rain, we also track rainfall over the land that feeds each river (the Alps for the Rhine and Danube, the Bohemian hills for the Elbe), comparing the last 45 days against seasonal normals, plus the 16-day rain forecast.

What the percentage means. For each month we publish the chance that a sailing day hits trouble. A day counts as trouble when the water falls below a line set from that stretch's own history: the level at which, in past years, low water was declared and ships struggled. The Seine is the mirror image. It is locked and rain-fed, so its risk is too much water, and its line sits at the top of its history rather than the bottom.

The live forecast where it reaches, history where it doesn't. Months within the forecast's seven-month reach use it; those are marked with a dot. Beyond that, the number is how often that month hit trouble across the last thirty years. Every number on the site is recomputed when the data refreshes. Nothing is hand-set.

The limits. We check the model against real low-water years so it tracks the actual channel, but the final call on whether a ship sails belongs to its captain. Cruise lines differ: newer ships sit shallower, and some reroute earlier than others, so the same river can treat two cruises differently. Weather beyond two weeks is a matter of odds. A 60% October is a strong warning, not a certainty. We publish the exact number and never round it toward a story.

Numbers last updated 2026-08-12. Independent: no cruise line pays to be here, none can influence a number, and we sell nothing.