The föhn (German) is a generic term for warm strong and often very dry downslope winds that descend in the lee of a mountain barrier. Originally applied to winds in the European Alps region, the term is now used for all similar winds. Föhn type winds (such as the chinook or the helm wind) are known for their rapid temperature rise, their desiccating effect and the rapid disappearance of snow cover.

Source: WeatherOnline.