The average annual rainfall ranges from very low in the northern and southern fringes of the desert to nearly non-existent over the central and the eastern part. The thin northern fringe of the desert receives more winter cloudiness and rainfall due to the arrival of low pressure systems over the Mediterranean Sea along the polar front, although very attenuated by the rain shadow effects of the mountains and the annual average rainfall ranges from 100 millimetres (4 in) to 250 millimetres (10 in). For example, Biskra , Algeria and Ouarzazate , Morocco are found in this zone. The southern fringe of the desert along the border with the Sahel receives summer cloudiness and rainfall due to the arrival of the Intertropical Convergence Zone from the south and the annual average rainfall ranges from 100 millimetres (4 in) to 250 millimetres (10 in). For example, Timbuktu, Mali and Agadez , Niger are found in this zone. The vast central hyper-arid core of the desert is virtually never affected by northerly or southerly atmospheric disturbances and permanently remains under the influence of the strongest anticyclonic weather regime, and the annual average rainfall can drop to less than 1 millimetre ( in). In fact, most of the Sahara receives less than 20 millimetres ( in). Of the 9,000,000 square kilometres (3,500,000 sq mi) of desert land in the Sahara, an area of about 2,800,000 square kilometres (1,100,000 sq mi) (about 31% of the total area) receives an annual average rainfall amount of 10 millimetres ( in) or less, while some 1,500,000 square kilometres (580,000 sq mi) (about 17% of the total area) receives an average of 5 millimetres ( in) or less.  The annual average rainfall is virtually zero over a wide area of some 1,000,000 square kilometres (390,000 sq mi) in the eastern Sahara comprising deserts of: Libya, Egypt and Sudan ( Tazirbu , Kufra , Dakhla , Kharga , Farafra , Siwa , Asyut , Sohag , Luxor, Aswan, Abu Simbel , Wadi Halfa) where the long-term mean approximates millimetres ( in) per year.  Rainfall is very unreliable and erratic in the Sahara as it may vary considerably year by year. In full contrast to the negligible annual rainfall amounts, the annual rates of potential evaporation are extraordinarily high, roughly ranging from 2,500 millimetres (100 in) per year to more than 6,000 millimetres (240 in) per year in the whole desert.  Nowhere else on Earth has air been found as dry and evaporative as in the Sahara region. However, at least two instances of snowfall have been recorded in Sahara, in February 1979 and December 2016, both in the town of Ain Sefra . 
"wasteland," early 13c., from Old French desert (12c.) "desert, wilderness, wasteland; destruction, ruin," from Late Latin desertum (source of Italian diserto , Old Provençal dezert , Spanish desierto ), literally "thing abandoned" (used in Vulgate to translate "wilderness"), noun use of neuter past participle of Latin deserere "forsake" (see desert (v.)).
Sense of "waterless, treeless region" was in Middle English and gradually became the main meaning. Commonly spelled desart in 18c., which is not etymological but at least avoids confusion with the other two senses of the word. Classical Latin indicated this idea with deserta , plural of desertus .
In addition, other elements conspire to take away from the harvest for which we worked so hard to produce. Despite the best application of modern agricultural practices, an unavoidable portion of what is grown rots in the fields prior to harvest time, or in the world’s storage bins afterwards. Every year, depending upon geographic location and intensity of El Niño events, crops suffer from too little water and wither on the spot, or are lost to severe flooding, hailstorms, tornados, earthquakes, hurricanes, cyclones, fires, and other destructive events of nature. Many of these phenomena are at best difficult to predict, and at worst are impossible to react to in time to prevent the losses associated with them. In sub-Saharan Africa, locusts remain an ever-present threat (42), and can devastate vast areas of farmland in a matter of days. Even after a bumper crop is realized, problems associated with processing and storage lessen the actual tonnage that is available to the consumer. A large portion of the harvest, regardless of the kind of plant or grain, is despoiled or a portion consumed by a variety of opportunistic life forms (., fungi, bacteria, insects, rodents) after being stored. While it is conceded that at present the abundance of cash crops is more than sufficient to meet the nutritional needs of the world’s human population, delivering them to world markets is driven largely by economics, not biological need. Thus, the poorest people – some billion – are forced to live in a constant state of starvation (43), with many thousands of deaths per year attributable to this wholly preventable predicament (44). Locating vertical farms near these human “hot spots” would greatly alleviate this problem.