Katabatic winds

A Katabatic wind, from the Greek word katabatikos meaning "going downhill", is the technical name for a drainage wind, a wind that carries high density air from a higher elevation down a slope under the force of gravity.

Such winds are sometimes also called fall winds. Katabatic winds can rush down elevated slopes at hurricane speeds. 

In the following photo taken early April 2013 while we tried to pass Fragokastelo it shows a katabatic (off shore) up to force 8/9. Not a good place to paddle!

Fragokastelo force 9 winds

A katabatic wind originates from radiational cooling of air atop a plateau, a mountain, glacier, or even a hill. Since the density of air is inversely proportional to temperature, the air will flow downwards, warming adiabatically as it descends. The temperature of the wind depends on the temperature in the source region and the amount of descent.

In the case of Crete, for example, the wind can (but does not always) become hot by the time it reaches sea level.
The wind is very dangerous as it is blowing off shore and in case of a capsize a rescue will be very difficult (some times impossible). Katabatic winds are something that you need to avoid!

Don't be fooled from the small waves when a katabatic wind comes, this is happening as waves need a bigger distance to build (2-4km due to high summits above 2000 meters / 6000 ft).