If you lie on the ground at night with no cover, you get cold rather quickly. Much of this is due to energy loss by radiation. At night in a dry climate, the temperature of the sky can drop to -40 degrees C. If you are lying on the ground with thin clothing that provides little insulation, the surface temperature of your skin and clothes will be about 30 degrees C.
Estimate the net rate at which your body loses energy by radiation to the night sky under these conditions. Hint: What area should you use?