Climate

The Sahara desert is home to one of the harshest climates in the world. Located in the trade winds belt, the region is subject to winds that are frequently strong and blow constantly from the northeast. The desiccating and dust-laden winds are sometimes felt north and south of the desert, where they are variously known as sirocco, khamsin, simoom, and harmattan. The northern slopes of the Atlas Mountains intercept most of the moisture from winds blowing inshore from the Mediterranean Sea.

Border zones on the north and south, where the desert merges with the steppe, receive about 10 in. (25 cm) of rain a year with some seasonal regularity, but over most of the region rainfall is sparser, with an average annual total of less than 5 in. (12.7 cm). Rainfall is usually torrential when it occurs after long dry periods that sometimes last for years. The region's low relative humidity rarely exceeds 30% and is often in the 4% to 5% range.

Daytime temperatures are high; Azizia, Libya holds the world's highest official temperature in the shade (136°F/58°C) in September 1922. Heat loss in the Sahara is rapid at night and a diurnal range of 86°F (30°C) is common. Freezing temperatures are not uncommon at night from December to February.