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 injustices caused by the Egyptian colonial administration: arbitrary imprisonments were cancelled, torture instruments were destroyed, and taxes were remitted. To enlist the support of the population, Gordon legalised slavery, despite the fact that he himself had abolished it a few years earlier. This decision was popular in Khartoum, but caused controversy in Britain. Gordon was determined to "smash up the Mahdi". He requested that a regiment of Turkish soldiers be sent to Khartoum as Egypt was still nominally a province of the Ottoman Empire. When this was refused, Gordon asked for a unit of Indian Muslim troops and later for