Source: The Library Of Congress Country Studies
Lebanon has a Mediterranean climate characterized by a long, hot, and dry summer, and cool, rainy winter. Fall is a transitional season with a gradual lowering of temperature and little rain; spring occurs when the winter rains cause the vegetation to revive. Topographical variation creates local modifications of the basic climatic pattern. Along the coast, summers are hot and humid, with little or no rain. Heavy dews form, which are beneficial to agriculture. The daily range of temperature is not wide, although temperatures may reach above 38° C in the daytime and below 16° C at night. A west wind provides relief during the afternoon and evening; at night the wind direction is reversed, blowing from the land out to sea.
Winter is the rainy season, with major precipitation falling after December. Rainfall is generous but is concentrated during only a few days of the rainy season, falling in heavy cloudbursts. The amount of rainfall varies greatly from one year to another. Occasionally, there are frosts during the winter, and about once every fifteen years a light powdering of snow falls as far south as Beirut. A hot wind blowing from the Egyptian desert called the khamsin (Arabic for fifty), may provide a warming trend during the fall, but more often occurs during the spring. Bitterly cold winds may come from Europe. Along the coast the proximity to the sea provides a moderating influence on the climate, making the range of temperatures narrower than it is inland, but the temperatures are cooler in the northern parts of the coast where there is also more rain.
In the Lebanon Mountains the gradual increase in altitude produces colder winters with more precipitation and snow. The summers have a wider daily range of temperatures and less humidity. In the winter, frosts are frequent and snows heavy; in fact, snow covers the highest peaks for much of the year. In the summer, temperatures may rise as high during the daytime as they do along the coast, but they fall far lower at night. Inhabitants of the coastal cities, as well as visitors, seek refuge from the oppressive humidity of the coast by spending much of the summer in the mountains, where numerous summer resorts are located. Both the khamsin and the north winter wind are felt in the Lebanon Mountains. The influence of the Mediterranean Sea is abated by the altitude and, although the precipitation is even higher than it is along the coast, the range of temperatures is wider and the winters are more severe.
The Biqa Valley and the Anti-Lebanon Mountains are shielded from the influence of the sea by the Lebanon Mountains. The result is considerably less precipitation and humidity and a wider variation in daily and yearly temperatures. The khamsin does not occur in the Biqa Valley, but the north winter wind is so severe that the inhabitants say it can "break nails." Despite the relatively low altitude of the Biqa Valley (the highest point of which, near Baalbek, is only 1,100 meters) more snow falls there than at comparable altitudes west of the Lebanon Mountains.
Because of their altitudes, the Anti-Lebanon Mountains receive more precipitation than the Biqa Valley, despite their remoteness from maritime influences. Much of this precipitation appears as snow, and the peaks of the Anti-Lebanon, like those of the Lebanon Mountains, are snow-covered for much of the year. Temperatures are cooler than in the Biqa Valley.
Data as of 1987