Down to -20°C at night: what are the “TAF” or cold holes, these places where it can be much colder than elsewhere ?

The cold can be more pronounced in some places. In the "cold holes", nighttime temperatures can drop below – 20 °C.

The best known are Mouthe, in Doubs, with its temperature record of -36.7°C recorded on January 13, 1968, or the Chamonix Valley. Cold holes “are places, often deep valleys in which, under certain weather conditions, cold air can accumulate and nighttime temperatures drop below -20°C”, underlines Météo-France.

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These areas are generally located far from any sea or ocean. This trend is reinforced by altitude.

How they form ?

Cold holes, or “TAFs,” form during winter anticyclonic conditions, with a weak easterly wind and clear skies, according to weather station professionals.

During the night, the air at ground level becomes colder than the air at altitude. The air in contact with this cold ground cools in turn. Cold air then accumulates.

In France… and elsewhere

The absence of vegetation, the presence of snow and “basins” particularly favor the formation of cold holes.

France is not the only country in Europe affected by TAF, specifies La Chaîne Météo. Places such as the Combe des Amburnex in Switzerland or the Cantabrian Mountains in northern Spain have recorded values ​​of up to -47°C and -38°C, although these have not been made official.