The climate which characterises the town was classified, in 2010, as a “frank oceanic climate” (French: climat océanique franc), according to the typology of climates of France [fr] which identified eight major types of climates in metropolitan France.[3] In 2020, the town was classified as having an “oceanic climate” type using the classification established by Météo-France, which only has five main types of climates for mainland France. This type of climate is characterised by mild temperatures and relatively abundant rainfall (in conjunction with disturbances from the Atlantic), distributed throughout the year with a slight maximum from October to February.[4]
The climatic parameters which made it possible to establish the 2010 typology include six variables for temperature and eight for precipitation, the values of which correspond to the monthly data for the 1971–2000 norm.[5] The seven main variables characterising the municipality are presented in the box below.
Municipal climatic parameters over the period 1971–2000[3]
- Average annual temperature: 12.3°C
- Number of days with a temperature below −5°C : 1.1 days
- Number of days with a temperature above 30°C : 3.3 days
- Annual thermal amplitude: 13°C[Note 1]
- Annual cumulative precipitation: 714mm
- Number of days of precipitation in January: 12.1 days
- Number of days of precipitation in July: 6.1 days
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These variables have evolved with climate change. A study carried out in 2014 by the General Directorate of Energy and Climate [fr],[6] supplemented by regional studies,[7] indeed predicts that the average temperature should increase and the average rainfall decrease, but with strong regional variations. These changes have been recorded on the nearest Météo-France meteorological station in Pornic, in service since 1919,[8] 10km north of Moutiers-en-Retz, where the mean annual temperature is 13°C and the rainfall is 738.1 mm for the period 1981–2010.[9] At the next closest historical meteorological station, "Nantes-Bouguenais", 31 km east inland of Moutiers-en-Retz in the town of Bouguenais, operational since 1945, the annual average temperature changes by 12.2 °C for the period 1971–2000,[10] 12.5 °C for 1981–2010, then 12.7 °C for 1991–2020.[11]
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