The single most reliable predictor of how a Bordeaux vintage turns out is the weather of the growing season. This is not a new idea — economists showed decades ago that a few seasonal weather variables explain a remarkable share of the differences between Bordeaux vintages and even their eventual prices. What is new is the quality and reach of the data now available to measure it.
The record we read
Foudre reads a reconstructed daily climate history for each Left-Bank estate going back to 1990, drawn from the European Copernicus programme's ERA5 reanalysis — the same gold-standard dataset used in climate research. For the season ahead, it reads a seasonal-forecast ensemble: not one forecast, but a spread of plausible outcomes, so the uncertainty is part of the answer rather than hidden from it.
Crucially, this data is downscaled to each château's location and elevation. A vineyard on a warm gravel rise by the Gironde does not experience the same season as one on cooler, lower ground a few kilometres away, and the numbers reflect that.
From raw weather to meaning
Raw temperatures and rainfall are not yet a vintage call. Foudre turns them into the metrics viticulturists actually use — growing-season warmth, harvest-window rainfall, the cool nights that preserve aromatics, heat spikes, spring-frost exposure — and scores those against a structured model of vintage quality built from the published literature.
Because the score is grounded in explicit, named signals rather than a black box, you can read why a year scores the way it does, and disagree with it intelligently.