Aswan extremity of Egypt, the river flows for more than without bar or cataract. The voyage from Aswan to Alexandria usually took 21 to 28 days in favourable weather. Aswan has a hot desert climate (Köppen climate classification "BWh") like the rest of Egypt. Aswan and Luxor have the hottest summer days of any city in Egypt. Aswan is one of the hottest, sunniest and driest cities in the world. Average high temperatures are consistently above during summer (June, July, August and also September) while average low temperatures remain above . Summers are long, prolonged and extremely hot. Average high temperatures
Aswan Dam mere 460 tons in 1968, but then gradually recovered to 8,590 tons in 1992. A scientific article in the mid-1990s noted that "the mismatch between low primary productivity and relatively high levels of fish production in the region still presents a puzzle to scientists." A concern before the construction of the High Dam had been the potential drop in river-bed level downstream of the Dam as the result of erosion caused by the flow of sediment-free water. Estimates by various national and international experts put this drop at between 2 and 10 meters. However, the actual drop has been measured