The climate of the Sahara Desert has remained quite consistent for the past 2000 years. It is the world's largest hot desert and one of the driest places on the planet. Some parts of the Sahara get less than 2 centimetres of rainfall each year (0.79 inches). It is one of the harshest climates in the world.
The average rainfall for the Sahara Desert as a whole is less than 5 inches per year (12.7 centimetres). The driest areas receive less than 2 centimetres or rain and the wettest areas get up to 10 centimetres or just under 4 inches of rainfall. It does not rain often and when it does it is usually a torrential downpour.
It is not uncommon for parts of the Sahara to go for up to seven years with no rain falling at all. When it does rain, children are often frightened, because they have never seen rain before. More common are sand storms and dust devils, funnel clouds of wind and sand.
The Sahara covers over 3,500,000 square miles (9,000,000 suare kilometres), making it about the same size as the continental United States or the continent of Europe. It covers most of Northern Africa stretching from the Atlantic coast to the Red Sea. The exact area of the desert isn't constant, as it shifts according to weather patterns over time.
International scientists believe that the Sahara is getting hotter, and that will make it even drier. Super-heated air over the desert becomes a sort of umbrella, evaporating the raindrops before they can even touch the ground. Clouds may form, and rain may be created but never add to the rainfall totals.
Rainfall is most frequent in the Sahara from December to March. However, the heaviest rains are more likely to occur in August than in any other month. When torrential rains fall they can cause flash floods and send water to parts of the desert that normally receive no precipitation as all.