Some deserts get more than 250mm of rainfall yearly but are still arid areas. For example, the Kalahari Desert gets up to a year. It has great sand dunes like the Sahara, but they do not shift in the winds. They have plants that anchor the sand and help to keep their shape. Other areas can also have more than 250mm of precipitation but lose more water via evapotranspiration than falls as precipitation. Tuscon and Alice Springs are good examples of this. Tucson gets an average of of rainfall a year. Alice Springs receives about yearly. Some scientists do not consider these as true deserts. 