<P> There are usually two or three variations of a desert climate: a hot desert climate (BWh), a cold desert climate (BWk) and, sometimes, a mild desert climate (BWh / BWn). Furthermore, to delineate "hot desert climates" from "cold desert climates", there are three widely used isotherms: either a mean annual temperature of 18 ° C (which is the most accurate and most commonly used), or a mean temperature of 0 ° C or − 3 ° C in the coldest month, so that a location with a "BW" type climate with the appropriate temperature above whichever isotherm is being used is classified as "hot arid" (BWh), and a location with the appropriate temperature below the given isotherm is classified as "cold arid" (BWk). </P> <P> To determine whether a location has an arid climate, the precipitation threshold is determined . The precipitation threshold (in millimetres) involves first multiplying the average annual temperature in ° C by 20, then adding 280 if 70% or more of the total precipitation is in the high - sun half of the year (April through September in the Northern Hemisphere, or October through March in the Southern), or 140 if 30--70% of the total precipitation is received during the applicable period, or 0 if less than 30% of the total precipitation is so received . If the area's annual precipitation is less than half the threshold, it is classified as a BW (desert climate). </P> <Table> <Tr> <Th> Sabha </Th> </Tr> <Tr> <Th> Climate chart (explanation) </Th> </Tr> <Tr> <Td> <Table> <Tr> <Td> J </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> J </Td> <Td> J </Td> <Td> </Td> <Td> </Td> <Td> O </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 7 19 6 </Td> <Td> 0 21 8 </Td> <Td> 10 26 12 </Td> <Td> 7 32 17 </Td> <Td> 36 22 </Td> <Td> 0 39 25 </Td> <Td> 0 39 25 </Td> <Td> 0 39 25 </Td> <Td> 0 38 24 </Td> <Td> 0 29 19 </Td> <Td> 26 12 </Td> <Td> 20 7 </Td> </Tr> <Tr> <Td_colspan="12"> Average max. and min . temperatures in ° C </Td> </Tr> <Tr> <Td_colspan="12"> Precipitation totals in mm </Td> </Tr> <Tr> <Td_colspan="12"> Source: World Weather Online </Td> </Tr> </Table> </Td> </Tr> <Tr> <Td> <Table> <Tr> <Th_colspan="12"> (show) Imperial conversion </Th> </Tr> <Tr> <Td> J </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> J </Td> <Td> J </Td> <Td> </Td> <Td> </Td> <Td> O </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 0.3 66 43 </Td> <Td> 0 70 46 </Td> <Td> 0.4 79 54 </Td> <Td> 0.3 90 63 </Td> <Td> 0 97 72 </Td> <Td> 0 102 77 </Td> <Td> 0 102 77 </Td> <Td> 0 102 77 </Td> <Td> 0 100 75 </Td> <Td> 0 84 66 </Td> <Td> 0 79 54 </Td> <Td> 0 68 45 </Td> </Tr> <Tr> <Td_colspan="12"> Average max. and min . temperatures in ° F </Td> </Tr> <Tr> <Td_colspan="12"> Precipitation totals in inches </Td> </Tr> </Table> </Td> </Tr> </Table> <Tr> <Th> Sabha </Th> </Tr>

What countries are in the arid climate zone