I don't think that black-body radiative transfer is a linear process.
The Stefan-Boltzman relation says power scales with the fourth power of temperature. So 1/3 absolute temperature would be 1/81 the inbound radiative energy. If you are getting 800W inbound at room temp, you would get 10W inbound at 100K (=300K/3).
Warm-blooded mammals of course have a reference point based on their thermal homeostatic capabilities (ability to maintain body temperature). “Warm” and “cold” is in relation to that.