Chinook or Foehn, strong wind which blows on the lee side of a mountain range, such as the Alps (where it is known as foehn), when stable air is made to flow over the range by a large-scale pressure gradient. The air is dry and warm at the foot of the mountains; the wind undergoes further heating and drying as it descends the slopes.

In early spring the winds melt the snow very quickly, but their effects are observable only in valleys, where the temperature increase due to compression is at its greatest. In America, the name is derived from the Chinook people, in whose territory the phenomenon was first observed.