Its maximum length is 4,800 km, running from west to east, and up to 1,200 km from north to south. Sahara covers most of Mauritania, Western Sahara, Algeria, Libya, Egypt, Sudan, Chad, Niger and Mali, and touches Morocco and Tunisia.
To the north, Sahara is bordered by the Atlas Mountains and the Mediterranean Sea; in the west by the Atlantic Ocean; in the south, the desert zone reaches 16º northern latitude; in the east it is bordered by the Nile. Still the desert continues to the east of the river until it reaches the Red Sea, but this is not considered a part of the Sahara.
Sahara is very dry but there is an annual rainfall in most regions, although just a few dozens of millimetre.
Sahara has a subtropical climate in its northern parts, and a tropical one in the south. Winters in the north are cold to cool; in the south, mild. Summers are hot all over the desert. The highest temperature every recorded is 58ºC in Aziziyah, Libya. There is very little rain in the northern parts, virtually nothing in the east, although more in the south. Most rain falls throughout the summer, followed by some scarce winter rain.
About a quarter of Sahara consists of mountains. The highest peak reaches 3415, being Emi Koussi in Chad. Some mountain peaks may even have snow in the winter. The main mountain ranges are Hoggar in Algeria; Aïr/Azbine in Niger; and Tibesti in Chad. The Sahara's lowest point lies in the Qattara Depression in Egypt, at about 130 metres below sea level.
Sand sheets and dunes represent about 25% of the Sahara; the other parts are mountains, stoney steppes and oases. Pyramidal dunes can be as high as 150 metres, while mountainous sand ridges as high as 350 metres.
There are several rivers running through the Sahara, of which the Nile River and Niger River are the only permanent ones. The rest being seasonal, involves that most of the time, there is only a dry river bed, which may carry water for brief periods following uncommon rainfalls. There may be years in between this happening.
Metallic minerals are very important to most Saharan countries. Algeria and Mauritania have several major deposits of iron ore, while smaller deposits are found in Egypt, Tunisia, Morocco, Western Sahara and Niger. Copper is found in Mauritania and manganese in Algeria. Small deposits of uranium are widely distributed in the Sahara, while Niger has the largest deposits. Phosphates are found in great quantities in Morocco and Western Sahara, and are already well-exploited. Algeria's phosphate production is smaller, but large enough for exports. Oil is mainly found in Algeria, and is of great importance to the economy of the entire country. While the mineral exploitation has led to economic growth in Sahara, this has rarely helped the indigenous population, as skilled workers have been brought in to the different fields.
Of the Sahara's around 4 million people, most live in Mauritania, Western Sahara, Algeria, Libya and Egypt. Dominant groups of people are Sahrawis, Tuareg and Negroids. The largest city is Nouakchott, Mauritania's capital. Other important cities are Tamanrasset in Algeria, and Sebha and Ghat in Libya.
Only 200,000 km² of Sahara are fertile oases, where dates, corn and fruits are grown. The few fertile regions today are fed by underground rivers and underground basins. Many of Sahara's oases rests in depressions (areas under sea level) allowing water to surface from underground reservoirs; artesian wells.
The soil in Sahara is low in organic matter, and often biologically inactive. The soil in depressions is often saline. Animal life is limited to gazelles, antelopes, jackals, foxes, badgers and hyena.
Other sorts of vegetation include scattered concentrations of grasses, shrubs and trees in the highlands, as well as in the oases and along river beds. Some plants are well adjusted to the climate, allowing them to germinate within 3 days of rain and sow their seeds within 2 weeks after that.
Animal life of Sahara include gerbil, jerboa, cape hare and desert hedgehog, barbary sheep, oryx, gazelle, deer, wild ass, baboon, hyena, jackal, sand fox, weasel and mongoose. The bird life counts more than 300 species.