A degree of frost is a non-standard unit of measure

Unit of measure

Unit of measure may refer to:* Units of measurement for relevance to weights and measures* Unit of account for relevance in economics* Unit of Measure , a 2000 album by Tony Rice...

 for air temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 meaning degree

Degree

-As a unit of measurement:* Degree symbol, , a notation used in science, engineering and mathematics* Degree , a unit of angle measurement* Degree in geographic coordinate system* Degree , a unit of temperature measurement...

s below melting point

Melting point

The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

 (also known as "freezing point") of water (32 degrees Fahrenheit

Fahrenheit

Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...

 or 0 degrees Celsius

Celsius

Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...

). "Degree" in this case can refer to degree Celsius  or Fahrenheit

Fahrenheit

Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...

.

When based on Celsius, 0 degrees of frost is the same as 0°C, and any other value is simply the negative of the Celsius temperature. When based on Fahrenheit, the conversion is a bit more complicated, as 0 degrees of frost is equal to 32°F. Conversion formulas:

• T [degrees of frost] = 32°F - T [°F]
• T [°F] = 32°F - T (degrees of frost)

Example: 5 degrees of frost equals 32°F - 5°F = 27°F.

The term 'degrees of frost' was widely used in Apsley Cherry-Garrard

Apsley Cherry-Garrard

Apsley George Benet Cherry-Garrard was an English explorer of Antarctica. He was a survivor of the Terra Nova Expedition and is acclaimed for his historical account of this expedition, The Worst Journey in the World....

's account of his Antarctic adventures in "The Worst Journey in the World". He recorded 109.5 (Fahrenheit) degrees of frost (-77.5 °F or -60.8 °C).