The question of the most rainy place in France pop up regularly in conversations. Actually, many places seem acceptable according to the calculation method. Which one answers this question the best? The place with most rain days? The one with the most cumulated rainfalls? Or the place with the longest rain times? Looking at data from the French agency for weather information Météo France can help us to find the most rainy place in France.
Météo France data
Météo France freely publishes surface synoptic observations on their portal. Data covers 62 meteorological stations in metropolitan and overseas France. Mostly hosted in airports, station updates informations every 3 hours since January 1st, 1996. Available fields include temperature, rainfalls, cloud cover, humidity and many more factors . But with a French territory of 672,051 square kilometers, 62 stations can only give a global picture of the differents climates in France. Morevover, only 8 stations lie at more than 300 meters of altitude. Yet, more rainfalls occur at higher altitudes .
Keeping these bias in mind, a simple yet efficient way to find the most rainy place in France remains to sum up every rainfalls from 1996 to today. More than the most rainy place in France, we will find here the place with the most recorded rainfalls. For clarity, only rainfalls from January 1st, 1996 to December 31th, 2017 enter in the computation.
The most rainy place in France
And at the top of the ranking lies Cayenne airport, the capital city of Guyane, an overseas department of France in South America. With 70,319 millimeters (Or 70 meters) of rainfalls from 1996 to 2017, it indeed rains a lot in Cayenne. The city lies full on the Intertropical Convergence Zone, one of the most rainy part in the world.
In metropolitan France
The Brest airport in Bretagne recorded the most rainfalls in metropolitan France. 26,620 millimeters from 1996 to 2017, or 26.6 meters. The region fame mostly lies in its delicious crêpes, beautiful landscapes and relative humidity.
And the dryest place in France?
Where does it rain the least in France? According to the Météo France surface synoptic observations, it rains the least at the Marignanne airport, next to Marseille. Only 10,965 millimeters, or 10 meters of rainfalls recorded from 1996 to 2017. Indeed, tourists usually praise the French riviera soft climate. But not so soft. Floods coming from the close moutains sometimes threaten the region in Autumn .
Source code for this article is available on Git.
 Manual on codes, Secretariat of the World Meteorological Organization, Geneva, Switzerland, 2009. https://library.wmo.int/pmb_ged/wmo_306-v1-1-2015_fr.pdf.
 D. Fowler, J. Cape, I. Leith, T. Choularton, M. Gay, A. Jones, The influence of altitude on rainfall composition at great dun fell, Atmospheric Environment. 22 (1988) 1355–1362. http://nora.nerc.ac.uk/id/eprint/6636/.
 E.J. Anthony, M. Julian, Source-to-sink sediment transfers, environmental engineering and hazard mitigation in the steep var river catchment, french riviera, southeastern france, Geomorphology. 31 (1999) 337–354. https://www.sciencedirect.com/science/article/pii/S0169555X99000884.