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what does it change for the forecasts

The seasonal normals are the average annual temperatures that are calculated over a period of 30 years and they are regularly updated by Météo-France to stick as closely as possible to the current climate, and to be able to characterize exceptional meteorological events as faithfully as possible. So this update has just been done.

>> “Châteauroux today is Agen thirty years ago”: why Météo France is updating its seasonal normals

From now on, Météo-France no longer relies on the average temperatures measured between 1981 and 2010 but on those recorded between 1991 and 2020. The reference period is therefore shifted by ten years as we get closer to us. This update of the seasonal normals shows a slightly different France: warmer, with shorter frost periods and drier soils.

This rise in average temperatures can be seen everywhere, especially in autumn and spring, but it is more marked in the Grand Est and Burgundy-Franche-Comté. The Grand Est is also more marked than the rest of France by a drop in precipitation. A drying out of the soil that can also be seen in the Massif Central.

Other regional developments over the past ten years: the number of days and the depth of snow cover have fallen in the mountain ranges, including the Alps. There are also eight to ten days less frost on average, in Troyes Poitiers, Chambéry or Lyon. And on the other hand, the number of hot days or nights over 20°C is increasing in the south-east: especially in Nîmes, Marseille, Lyon and Corsica.

Locally, the evolution of certain averages can sometimes be linked to the evolution of the number of meteorological stations, explains Mathieu Sorel, climatologist at Météo France. The evolution of the normals is indeed the sign of an ongoing climatic evolution.

On the scale of France, the average annual temperature has increased by more than 1°C in the space of 60 years. If we constantly update the seasonal normals, there is no risk of erasing the extent of this climate change because it is always quantified by taking the same benchmarks: either the pre-industrial era, or – closer to us – the period 1961- 1990. These references – which are those of the World Meteorological Organization – do not change.

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