It's -196.1500 degrees Celsius.

The Kelvin temperature scale was the brainchild of Belfast-born British inventor and scientist William Thomson — also known as Lord Kelvin. It is one of the three best-known scales used to measure temperature, along with Fahrenheit and Celsius.

Like other temperature scales, the freezing and boiling points of water are factors in establishing the scale’s range. There are 100 degrees between the temperate at which water freezes at (273.16 K) and boils (373.16 K).

Each unit on this scale, called a Kelvin rather than a degree, is equal to a degree on the Celsius scale. For this reason, just the K, not the degree symbol, is used when reporting temperatures in Kelvin. There are no negative numbers on the Kelvin scale, as the lowest number is 0 K.

Celsius is a measurement of temperature in which 0 degrees represents the freezing point of water, and 100 degrees represents water’s boiling point at the standard atmosphere, which is the mean barometric pressure at the mean sea level.

This temperature scale was developed by Swedish astronomer Anders Celsius in 1742.

Celsius performed diligent experiments to develop his scale, although he originally had 0 as the boiling point and 100 as the freezing point. In his paper, "Observations of two persistent degrees on a thermometer," he documented experiments to determine that water’s freezing point is independent of latitude or atmospheric pressure.