Arles is a Mediterranean climate with long summer, hot and dry, mild winters, lots of sunshine and erratic rainfall. Its climate includes features related to the geographical situation of the city south of the Rhone Valley between Cevennes and southern Alps. And fall, and to a lesser extent the periods April-early May, are watered with rainfall brief but important and sometimes harsh winters because of the Mistral wind and cold that gives them exceptional brightness Arles landscape. In winter temperatures drop below zero frequently over periods sometimes exceeding several weeks. One may recall the winters 1929, 1944, 1956, 1963, 1986 with records around -15 to -18 ° C. Conversely, 1 August 2001, at the Tour de Valat Arles station, was recorded a temperature of 38.7°C.
Rainfall Mediterranean are related to depression formed over the Gulf of Genoa off the Balearic Islands. Winds from east to south-east hot, loaded with water since crossing the Mediterranean meet the obstacle of the Cevennes, or less often, the Alps, rise into contact with cold air altitude cumulus nimbus enormous and sometimes erupt into brutal storms. The location of rain varies according to the respective location of the anticyclone and depression and their intensity depends on the volume of cloud created by the winds and humidity are of course differences in temperature. These storms generally occur in autumn and may cause precipitation of 200 mm per day and sometimes more. Duration of a few hours, they are often violent, such as 4 and Thursday 11 September 2008 where there were over 50 mm in less than an hour! The monthly rainfall also exhibits great variability. However, the annual rainfall is only 524 mm, one of the lowest in France and number of rainy days (+ 1 mm / day) for approximately 60 days per year. But this average hides a variable annual rains very important and the numbers range from 344 mm in 1945 to 1 063 mm in 1960, variations of more than 200%. The statistics also reveal that the dry or very dry periods may span two or three years, as between 1945 and 1947.