The dry regions are plagued by sandstorms, known as haboob, which can completely block out the sun. In the northern and western semi-desert areas, people rely on the scant rainfall for basic agriculture and many are nomadic, travelling with their herds of sheep and camels. Nearer the River Nile, there are well-irrigated farms growing cash crops. The sunshine duration is very high all over the country but especially in deserts where it could soar to over 4,000 h per year.