Strong, cold, dry and squally northerly wind that blows offshore with great frequency along the Mediterranean coast from northern Spain to northern Italy, and that is particularly frequent in the lower Rhone valley in south-eastern France blowing way out into the Golfe du Lion. The wind may persist for several days, and is best developed when a depression is forming in the Gulf of Genoa to the east of a ridge of high pressure. It might also be a purely katabatic wind. The airstream that feeds the mistral is commonly derived from polar air of maritime origin. It is most violent in winter and spring and its strenght is increased by the funneling effect of the Rhone valley.
The mistral might easily reach a speed of 130kph (75 knots) over the Rhone delta, compared with the typical 40 knots experienced along the coast.