Why does rainfall decrease from Algeria’s coast toward the Sahara?

The decrease in rainfall from Algeria’s coast toward the Sahara is primarily driven by the country's physical geography and atmospheric patterns.

Northern Algeria’s relief, characterized by mountain ranges running parallel to the coastline, acts as a barrier that limits the southward penetration of the Mediterranean climate. The coastal mountains are directly exposed to humid winds blowing inland from the Mediterranean, which results in higher precipitation in these littoral regions. However, as these air masses move southward and cross the Atlas ranges, the moisture is largely depleted, leading to a significant reduction in rainfall.1

Beyond these mountains, the atmosphere becomes increasingly dry. The High Plateau experiences insufficient precipitation, and the transition into the Sahara proper is marked by a further decline in annual rainfall to less than 4 inches (100 mm). This arid environment is further influenced by the sirocco, a hot, dry, and desiccating wind that blows seasonally from the Sahara toward the north, reinforcing the region's overall lack of moisture.1