• B – 70 % or more of the total annual rainfall is during the summer half of the year and r (r = average total annual precipitation in mm) is less than 20t + 280 (t = average annual temperature in °C), or 70 % or more of total annual precipitation is during the winter half of the year and r is less than 20t, or no half of the year has less than 70 % of total annual rainfall and r less than 20t + 140. Summer half of the year in the Northern hemisphere is from April to September, on the Southern hemisphere from October to March.
• W - r is less than the upper limit for B type classification parameter
• k - t is lower than 18 °C

The desert climate is characterized by extremely small rainfall. In general it includes areas, which have such little precipitation, that there is hardly any vegetation at all.

The total annual precipitation is at most 250 mm, but quite often much less and regions with no rainfall during the entire year are not an exception. In specific cases this climate type is also assigned to places with more than 250 mm of rainfall annually, but where more water is lost by evapotranspiration than falls with rain (for example some parts in Arizona).

Although the climate type has the word “cold” in it, this term is rather relative. Summers can still be very and sometimes extremely hot (temperatures, however, do not reach such high values as in the case of hot desert climate type BWh). What is different from the BWh type is the occurrence of also colder periods, sometimes extremely cold with temperatures well below freezing point.

Basically all regions with this climate type are found in Asia . Usually in the lee of high mountain ranges, often at high altitudes. The most well-known region with this climate type is probably the Asian Gobi desert in Mongolia. Summers are very hot, while winters extremely cold, the annual temperature range is very high and the same is true for the day/night temperature differences as well. Apart from central Asia (Mongolia, China, India), the BWk climate is also assigned to some parts in Western USA and South America.