Mont Ventoux is an essential meteorological marker for the surrounding population who studies the cloudy cap or mantle that hides its summit for nearly two hundred days a year to forecast the weather to come. The summit of Mont Ventoux is also swept by frequent winds that blow on average two days out of three at a speed faster than 56 mph (90 km/h) with a double record of 198.8 mph (320 km/h) on February 15 and November 19, 1967. The most renowned wind, the white mistral, descends along the Rhône valley and gives a bright blue sky. The black mistral and its easterly returns are responsible for a cloudy sky, while the marin, a southerly wind, brings rain.