The basalt lava at Kilauea has been measured at 1,160°C which is equivalent to 1453,15 K.
The Kelvin temperature scale is based on absolute zero, the temperature at which all thermal motion is stoped. The Kelvin (K) is official unit for temperature in International System of Units (SI).
The Celsius scale is based on freezing point of the water. The equation that connect these two scales is K=C+273.15, where C is temperature in Celsius and K is temperature in Kelvin. In other word the -273.15°C is absolute zero temperature or 0K.