The Meltemi wind was known by the old Greek as the Etesian northern winds, and results from a high pressure system (>1025) laying over the Balkan/Hungary area and a relatively low pressure (<1010) system over Turkey.

Although this katabatic wind can bring about harsh sailing conditions it also provides cooling, low humidity and good visibility. Furthermore, it can be characterized as one of the few Mediterranean winds that do not necessarily die out at the end of the day and can easily last more than three to six days. See my climate page for Greek weather statistics.
The onset is the monsoonal effect of the summer season that leads to the development of an intense heat trough over southern Asia extending westward over the Anatolian plateau. Higher pressure dominates over the relatively cooler surface of the Mediterranean Sea, and settled, dry weather persists. Northerly winds prevail along the Greek coast during the winter also, but only those northerly winds occurring between May and November are considered Etesian. The pressure gradients necessary to drive the Meltemi result from a combination of:
• The monsoonal effect during the summer that leads to a low pressure trough over Turkey. Etesian winds flow from a high pressure ridge over the Balkans toward the trough. During a strong Etesian, the trough may extend relatively far to the west and beyond Rhodes. It may also form a closed low, resulting in almost calm winds at Rhodes.
• Synoptic conditions leading to anti-cyclogenesis over the Balkans.
• A jet-effect wind increase caused by channelling of the wind between islands and mountain valleys. These effects tend to render wind reports from certain locations unrepresentative. In the lee of Crete, katabatic flow off the mountains generates gusty winds similar to the Föhn of the Alps. The mountain valleys tend to channel the flow which increases the wind velocity.

Usually blows with force up to 7 during the afternoon and slows 1-2 force or dies after sundown.