The lowest of the soil-temperature classes for family groupings of soils in the soil taxonomy system, applied to soils in temperate regions. The assessment of soil temperature is based on the mean annual temperature, and on the difference between mean summer and mean winter temperature, measured at a depth of 50 cm or at the surface of the underlying rock, whichever is shallower. In order of ascending temperature, the higher-temperature classes in temperate-region soils are called cryic, frigid, mesic, thermic, and hyperthermic, and in tropical regions the scale from cold to hot is isofrigid, isomesic, isothermic, and isohyperthermic.