Editing Desert climate (section)

==Precipitation==
Although no part of Earth is known for certain to be rainless, in the [[Atacama Desert]] of northern Chile, the average annual rainfall over 17 years was only {{convert|5|mm}}. Some locations in the [[Sahara Desert]] such as [[Kufra]], [[Libya]], record an even drier {{cvt|0.86|mm}} of rainfall annually. The official weather station in [[Death Valley]], United States reports {{cvt|60|mm}} annually, but in 40 months between 1931 and 1934 a total of just {{cvt|16|mm}} of rainfall was measured.

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 summer 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 there. If the area's annual precipitation is less than half the threshold (50%), it is classified as a ''BW'' (desert climate), while 50–100% of the threshold results in a [[semi-arid]] climate.<ref name="peel et al"/>