France's climate map is eight numbers wide

The obvious way to pick a warm French commune is to open the climate layer and read the number. It is a real number, drawn from the official +2.7°C warming scenario, and it is the same number for thousands of communes at once.

Metropolitan France has 34,832 communes on the map. Between them they carry eight distinct temperature values, because the scenario publishes eight stations and every commune inherits one of them. Two of the eight sit 0.01°C apart, which is a station artefact rather than a climate difference.

Eight values, 34,832 communes

One value — 12.14°C, the Paris basin and the north — covers 6,729 communes and 20.6 million people across 16 departments. Inside a band the layer separates nothing: two communes an hour apart read identical, because they answer to the same station.

The warmest band is not the dearest

Cross the bands with transaction prices and the ranking breaks. The Mediterranean band, at 17.44°C, has a median of 2,166 euros per square metre. The Provence hinterland band, at 16.19°C, comes in higher at 2,240. And the coldest band of the eight is third dearest, at 1,828, because it contains Paris.

Temperature is not what is being priced. Proximity to Paris, to the coast and to the ski valleys is, and the climate layer cannot see any of the three.

What this figure cannot tell you

It is an annual mean, so it carries no winter and no summer. Sunshine hours, frost days, August peaks and the mistral are all absent from it. A mild annual average can be a gentle winter or a punishing July, and this number will not say which.

It is also a projection rather than a forecast — the +2.7°C pathway is one assumption about the century, not a prediction about your retirement.

Use it for what it can do. Open the climate layer, add property price, and read the eight bands as a north-south sort. Choosing between two towns needs a weather station, not a map layer.