Katabatic winds are cold winds that become very strong as they descend mountains. The bora, which blows down the Yugoslav mountains toward the Adriatic coast, the Japanese oroshi, and the williwaw in Alaska are katabatic winds. The mistral, a dry, cold wind that blows for more than 100 days per year in southeast France, starts in the peaks of the Alps. As it descends toward the Rho?ne Valley, it strengthens, reaching up to 180 km/h by the time it arrives at the Mediterranean Sea.