Khartoum main Nile ("see map, upper right") as it zigzags through northern Sudan into Egypt at Lake Nasser. Khartoum is relatively flat, at elevation , as the Nile flows northeast past Omdurman to Shendi, at elevation about away. Under Köppen's climate classification system, Khartoum features a hot arid climate, with only the summer months seeing noticeable precipitation. The city averages a little over of precipitation per year. Based on annual mean temperatures, the city is one of the hottest major cities in the world. Temperatures routinely exceed in mid-summer. Its average annual high temperature is , with six months of the
Siege of Khartoum to the north by the Blue Nile and to the west by the White Nile. To defend the river banks, he created a flotilla of gunboats from nine small paddle-wheel steamers, until then used for communication purposes, which were fitted with guns and protected by metal plates. In the southern part of the town, which faced the open desert, he prepared an elaborate system of trenches, makeshift Fougasse-type land mines, and wire entanglements. Also, the surrounding country was controlled by the Shagia tribe, which was hostile to the Mahdi. By early April 1884, the tribes north of Khartoum rose in