Indice forêt météo

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The indice forêt météo (IFM) is an estimation of the risk of wildfire computed by Météo France, the French national meteorology institute; it means Forest weather index. It was created in 1992 and is based on a Canadian empirical model developed in 1976.

The index is a whole number that ranges between 0 and 20, 20 being the maximum risk. it is computed from:

the humidity of the air at the beginning of the afternoon (when it has its lowest value);
the temperature in the middle of the afternoon (when it has its highest value);
the precipitations during 24h (from noon to noon) ;
the maximum speed of the average wind.

This index is computed for 40 zones of France, three are in the Landes (département with the biggest forest of France).

Météo France sends the IFM to civil defense authorities, which allows the prepostioning of men and vehicles, especially air units.

The computed index is revised every year to take new data into account.